Method and apparatus for supporting handover

Abstract

According to embodiments of the present disclosure, a method and device supporting handover are provided. The method comprises: receiving a message from a destination base station central unit control plane entity; receiving data packets from a source base station; and discarding a packet data convergence protocol (PDCP) service data unit (SDU) containing a PDCP sequence number (SN) in the received data packets according to an indication of the message. The problem of coordination between the source base station and the destination base station during the handover process can be solved. In particular, in the case that the source base station and / or the destination base station support control plane and data plane separation, it is ensured that the source base station central unit control plane entity, the source base station central unit user plane entity, the destination base station central unit control plane entity and / or the destination base station central unit user plane entity can fully coordinate.

Description

TECHNICAL FIELD

[0001] The present application relates to the wireless communication technology, and particularly relates to a method and device supporting handover. BACKGROUND

[0002] To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a 'Beyond 4G Network' or a '5G Network'.

[0003] Wireless communication is one of the most successful innovations in modern history. Recently, the number of subscribers to wireless communication services has exceeded 5 billion and is continuing to grow rapidly. As smartphones and other mobile data devices (e.g., tablet computers, notebook computers, netbooks, e-book readers, and machine-type devices) are increasingly popular among consumers and enterprises, demand for wireless data services is rapidly growing. In order to meet the high-speed growth of mobile data traffic and support new applications and deployments, it is essential to improve the efficiency and coverage of the wireless interface.

[0004] The base station can contain a base station central unit control plane entity and a base station central unit user plane entity.

[0005] When a UE moves between two base stations, in order to ensure the continuity of services, it is necessary to define a handover procedure, including intra-system handover such as inter-gNB handover, inter-gNB and eNB connected to 5GC handover, and also inter-system handover such as inter-5G system (5GS) and evolved packet system (EPS) handover. SUMMARY

[0006] TECHNICAL PROBLEM

[0007] For data forwarding, how the source base station and the target base station coordinate work is currently a problem. In particular, in the case where the source base station and / or the target base station support control plane and data plane separation, how to ensure that the source base station central unit control plane entity, the source base station central unit user plane entity, the target base station central unit control plane entity, and / or the target base station central unit user plane entity can fully coordinate work is currently a problem.

[0008] TECHNICAL SOLUTION

[0009] According to an aspect of an embodiment of the present application, a method of supporting handover is provided, comprising: receiving a message from a target base station central unit control plane entity; receiving data packets from a source base station; and discarding a packet data convergence protocol (PDCP) service data unit (SDU) containing a PDCP sequence number (SN) in the received data packets according to an indication of the message.

[0010] In one example, the indication of the message includes indication information sent through a bearer context modification request message, the indication information indicating at least one of: full configuration or differential configuration; whether PDCP SN is preserved; whether PDCP is restarted; and whether to discard PDCP SDUs containing PDCP SN.

[0011] In one example, discarding PDCP SDUs containing PDCP SN in the received data packets according to the indication of the message includes discarding PDCP SDUs containing PDCP SN in the received data packets when the indication information indicates at least one of: full configuration; PDCP SN is not preserved; PDCP is restarted; and discarding PDCP SDUs containing PDCP SN.

[0012] In one example, the indication of the message includes at least one of: no PDCP SN status information is received; no PDCP SN status information of a data radio bearer (DRB) is received; no bearer context modification request message is received; and no PDCP SN status information of the DRB is included in the received bearer context modification request message.

[0013] In one example, discarding PDCP SDUs containing PDCP SN includes identifying the SDUs to be discarded according to SN in a general packet radio service (GPRS) tunneling protocol (GTP) user plane (GTP-U) packet.

[0014] In one example, the received data packets are sent by a source base station or are forwarded by a core network from a source base station.

[0015] In one example, PDCP SDUs without PDCP SN in the received data packets are new data.

[0016] According to another aspect of embodiments of the present application, there is provided a method of supporting handover, comprising: receiving a handover request message; receiving a sequence number (SN) status transfer message or a downlink radio access network (RAN) status transfer message; and sending a message to a destination base station central unit user plane entity, wherein the destination base station central unit user plane entity discards PDCP service data units (SDUs) containing PDCP sequence numbers (SNs) in received data packets according to an indication of the message.

[0017] In one example, receiving the handover request message includes receiving the handover request message from a source base station, and receiving the SN status transfer message includes receiving the SN status transfer message from the source base station, wherein the handover request message is an Xn application protocol (AP) message or other inter-base station message, and wherein the SN status transfer message is an Xn AP message or other inter-base station message.

[0018] In one example, receiving the handover request message includes receiving the handover request message from the core network, wherein the handover request message received from the core network is a Next Generation Application Protocol, NGAP, message or other message between the base station and the core network.

[0019] In one example, the handover type is included in the handover request message received from the core network.

[0020] In one example, the method further includes deciding whether to use full configuration or differential configuration.

[0021] In one example, sending the message to the destination base station central unit user plane entity includes sending a bearer context modification request message to the destination base station central unit user plane entity when the handover type is inter-system handover or when it is decided to use full configuration.

[0022] In one example, the indication of the message includes indication information sent through the bearer context modification request message, the indication information indicating at least one of: full configuration or differential configuration; whether PDCP SN is preserved; whether PDCP is restarted; and whether to discard packets containing PDCP SN of PDCP SDU.

[0023] In one example, the indication of the message includes at least one of: no PDCP SN status information is received; no PDCP SN status information of data radio bearer, DRB, is received; no bearer context modification request message is received; and no PDCP SN status information of DRB is included in the received bearer context modification request message.

[0024] According to an aspect of embodiments of the present application, there is provided a method of supporting handover, comprising: receiving, by a destination base station, a handover request message; sending, by the destination base station, information about full configuration or differential configuration to a source base station; and not sending, by the source base station, a packet data convergence protocol, PDCP, service data unit, SDU, containing a PDCP sequence number, SN, to the destination base station based on the information.

[0025] In one example, receiving the handover request message by the destination base station includes receiving the handover request message from the source base station or the core network, and the handover request message received from the source base station is an Xn application protocol, AP, message or other inter-base station message, and the handover request message received from the core network is a Next Generation Application Protocol, NGAP, message or other message between the base station and the core network.

[0026] In one example, the method further includes deciding, by the destination base station, whether to use full configuration or differential configuration, the full configuration or differential configuration being per data radio bearer.

[0027] In one example, when the source base station supports source base station central unit user plane and source base station central unit control plane separation, the source base station central unit control plane entity informs the source base station central unit user plane entity not to send PDCP SDUs containing PDCP SNs to the target base station.

[0028] In one example, the source base station central unit control plane entity informing the source base station central unit user plane entity not to send PDCP SDUs containing PDCP SNs to the target base station includes the source base station central unit control plane entity sending an indication information to the source base station central unit user plane entity, the indication information indicating at least one of: full configuration or differential configuration; whether PDCP SN status is preserved; whether only new data is sent; whether PDCP SDUs containing PDCP SNs are sent; whether PDCP packets sent to a user equipment (UE) that are not acknowledged by the UE are sent; and whether only PDCP SDUs not containing PDCP SNs are sent.

[0029] In one example, the source base station central unit control plane entity informing the source base station central unit user plane entity not to send PDCP SDUs containing PDCP SNs to the target base station includes the source base station central unit control plane entity sending a tunnel information for data forwarding to the source base station central unit user plane entity without requesting PDCP SN status information to indicate that the source base station central unit control plane entity does not send PDCP SN status information to the target base station.

[0030] According to an aspect of an embodiment of the present application, there is provided a method for supporting handover, comprising: receiving a handover related message; and indicating information for data forwarding to a source base station central unit user plane entity, wherein the source base station central unit user plane entity sends PDCP service data units (SDUs) not containing PDCP SNs to a target base station based on the information for data forwarding.

[0031] In one example, the handover related message is one of a handover request acknowledge message and a handover command message, and receiving the handover related message includes receiving the handover request acknowledge message from the target base station or receiving the handover command message from a core network, and wherein the handover related message indicates whether full configuration or differential configuration or indicates whether PDCP SN status is preserved.

[0032] In one example, the indicating information for data forwarding comprises sending indication information through a bearer context modification request message, and the indication information indicates at least one of: whether PDCP SN status is preserved; whether only new data is sent; whether PDCP SDUs containing PDCP SNs are sent; whether PDCP data packets sent to a user equipment (UE) that the UE has not acknowledged are sent; and whether only PDCP SDUs not containing PDCP SNs are sent.

[0033] In one example, the indicating information for data forwarding comprises sending channel information for data forwarding without requesting PDCP SN status information from a source base station central unit control plane entity to indicate that the source base station central unit control plane entity does not send PDCP SN status information to a destination base station.

[0034] According to an aspect of an embodiment of the present application, there is provided a method for supporting handover, comprising: receiving indication information for data forwarding; and based on the indication information for data forwarding, sending, to a destination base station, PDCP service data units (SDUs) not containing PDCP SNs.

[0035] In one example, the indicating information for data forwarding comprises receiving indication information through a bearer context modification request message, and the indication information indicates at least one of: whether PDCP SN status is preserved; whether only new data is sent; whether PDCP SDUs containing PDCP SNs are sent; whether PDCP data packets sent to a user equipment (UE) that the UE has not acknowledged are sent; and whether only PDCP SDUs not containing PDCP SNs are sent.

[0036] In one example, the receiving indication information for data forwarding comprises receiving channel information for data forwarding without requesting PDCP SN status information from a source base station central unit control plane entity to indicate that the source base station central unit control plane entity does not send PDCP SN status information to a destination base station.

[0037] According to another aspect of the embodiments of the present application, there is provided a method for supporting handover, comprising: receiving, by a target base station central unit control plane entity, a handover request message; sending, by the target base station central unit control plane entity, configuration information of source DRBs and configuration information of target DRBs, and / or mapping of source quality of service (QoS) flows to data radio bearers (DRBs) and mapping of target QoS flows to DRBs, to a target base station central unit user plane entity; and processing, by the target base station central unit user plane entity, forwarded data received from a source base station using the source DRB configuration and / or the source QoS flow to DRB mapping, and processing new data received from a core network using the target DRB configuration and / or the target QoS flow to DRB mapping.

[0038] In one example, the handover request message is received from a source base station or from a core network, the handover request message received from the source base station is an inter-base station interface application layer message, and the handover request message received from the core network is an application layer message of a base station and core network interface, the handover request message including configuration information of a user equipment (UE) at the source base station, the configuration information including mapping of QoS flows to DRBs.

[0039] In one example, when the target base station central unit control plane entity decides to use different mapping of QoS flows to DRBs than the source base station, the target base station central unit control plane entity temporarily configures the same mapping of QoS flows to DRBs as the source base station for processing forwarded data from the source base station.

[0040] In one example, the source end to be established Qos flow information is represented by the existing to be established Qos flow information in the to be established DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the destination end to be established Qos flow information is represented by a new information element; or the destination end to be established Qos flow information is represented by the existing to be established Qos flow information in the to be established DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the source end to be established Qos flow information is represented by a new information element; or the source end mapped to the DRB Qos flow is represented by the existing flow mapping information in the to be modified DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the destination end mapped to the DRB Qos flow is represented by a new information element; or the destination end mapped to the DRB Qos flow is represented by the existing flow mapping information in the to be modified DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the source end mapped to the DRB Qos flow is represented by a new information element.

[0041] In one example, the destination base station central unit control plane entity directly sends the configuration information of the source end DRB and the configuration information of the destination end DRB to the destination base station central unit user plane entity, or sends the configuration information of the destination end DRB and the differential configuration of the source end and the destination end to the destination base station central unit user plane entity, or sends the configuration information of the source end DRB and the differential configuration of the source end and the destination end to the destination base station central unit user plane entity.

[0042] According to another aspect of the embodiments of the present application, a method for supporting handover is provided, comprising: receiving a handover request message; and sending the configuration information of the source end DRB and the configuration information of the destination end DRB, and / or the mapping of the source end quality of service (Qos) flow to data radio bearer (DRB) and the mapping of the destination end Qos flow to DRB to a destination base station central unit user plane entity, wherein the configuration of the source end DRB and / or the mapping of the Qos flow to DRB is used by the destination base station central unit user plane entity to process the forwarded data received from a source base station, and the configuration of the destination end DRB and / or the mapping of the Qos flow to DRB is used by the destination base station central unit user plane entity to process the new data received from a core network.

[0043] In one example, the source end to be established Qos flow information is represented by the existing to be established Qos flow information in the to be established DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the destination to be established Qos flow information is represented by a new information element; or the destination to be established Qos flow information is represented by the existing to be established Qos flow information in the to be established DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the source to be established Qos flow information is represented by a new information element; or the source end to be mapped to the DRB Qos flow is represented by the existing flow mapping information in the to be modified DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the destination end to be mapped to the DRB Qos flow is represented by a new information element; or the destination end to be mapped to the DRB Qos flow is represented by the existing flow mapping information in the to be modified DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and the source end to be mapped to the DRB Qos flow is represented by a new information element.

[0044] In one example, the destination base station central unit control plane entity directly sends the configuration information of the source end DRB and the configuration information of the destination end DRB to the destination base station central unit user plane entity, or sends the configuration information of the destination end DRB and the differential configuration of the source end and the destination end to the destination base station central unit user plane entity, or sends the configuration information of the source end DRB and the differential configuration of the source end and the destination end to the destination base station central unit user plane entity.

[0045] According to still another aspect of the embodiments of the present application, a method for supporting handover is provided, comprising: receiving the source end DRB configuration information and the destination end DRB configuration information from the destination base station central unit control plane entity, and / or receiving the mapping of the source end quality of service (Qos) flow to data radio bearer (DRB) and the mapping of the destination end Qos flow to DRB from the destination base station central unit control plane entity; and processing the forwarded data received from the source base station by using the configuration of the source end DRB and / or the mapping of the Qos flow to DRB, and processing the new data received from the core network by using the configuration of the destination end DRB and / or the mapping of the Qos flow to DRB.

[0046] In one example, the destination base station central unit control plane entity and the base station central unit user plane entity interface message indicates the destination Qos flow information to be established by using the existing Qos flow information to be established in the information of the DRB to be established in the message, and indicates the source Qos flow information to be established by using a new information element; or indicates the source Qos flow information to be established by using the existing Qos flow information to be established in the information of the DRB to be established in the message, and indicates the destination Qos flow information to be established by using a new information element; or indicates the Qos flow of the destination mapped to the DRB by using the existing flow mapping information in the information of the DRB to be modified in the message of the base station central unit control plane entity and the base station central unit user plane entity interface message, and indicates the Qos flow of the source mapped to the DRB by using a new information element; or indicates the Qos flow of the source mapped to the DRB by using the existing flow mapping information in the information of the DRB to be modified in the message of the base station central unit control plane entity and the base station central unit user plane entity interface message, and indicates the Qos flow of the destination mapped to the DRB by using a new information element.

[0047] In one example, the destination base station central unit control plane entity directly sends the configuration information of the source DRB and the configuration information of the destination DRB to the destination base station central unit user plane entity, or sends the configuration information of the destination DRB and the differential configuration of the source and the destination to the destination base station central unit user plane entity, or sends the configuration information of the source DRB and the differential configuration of the source and the destination to the destination base station central unit user plane entity.

[0048] According to another aspect of the embodiments of the present application, a method for supporting handover is provided, comprising: a destination base station central unit control plane entity receiving a handover request message from a source base station or from a core network; the destination base station central unit control plane entity sending the mapping of the source quality of service (Qos) flow to data radio bearer (DRB) to the destination base station central unit user plane entity; the destination base station central unit user plane entity using the received mapping of the source Qos flow to DRB to process the forwarded data received from the source base station; the destination base station central unit control plane entity sending the mapping of the destination Qos flow to DRB to the base station central unit user plane entity; and the destination base station central unit user plane using the newly received mapping of the Qos flow to DRB to process the new data received from the core network and send to a user equipment (UE).

[0049] In one example, the method further comprises: the destination base station central unit control plane entity including the source Qos flow to DRB mapping in a handover command message sent to the UE through the source base station.

[0050] In one example, the method further comprises: the destination base station central unit control plane entity including the source Qos flow to DRB mapping in a handover command message sent to the UE through the source base station; the destination base station central unit control plane entity sending a radio resource control (RRC) reconfiguration message to the UE, the RRC reconfiguration message including the destination decided Qos flow to DRB mapping; the destination base station central unit user plane entity sending an indication message to the destination base station central unit control plane entity after the destination base station central unit user plane entity receives an end marker packet; and the destination base station central unit control plane entity sending the destination decided Qos flow to DRB mapping to the UE through the RRC reconfiguration message.

[0051] In one example, the destination base station central unit control plane entity sending the source service Qos flow to DRB mapping to the destination base station central unit user plane entity comprises: including the to-be-established Qos flow information in the to-be-established DRB information sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity, the to-be-established Qos flow information included in the to-be-established DRB information being set according to the source Qos flow to DRB mapping.

[0052] In one example, the destination base station central unit control plane entity sending the destination Qos flow to DRB mapping to the base station central unit user plane entity comprises: including the to-be-established Qos flow information in the to-be-established DRB information sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity, the to-be-established Qos flow information included in the to-be-established DRB information being set according to the destination Qos flow to DRB mapping.

[0053] According to another aspect of the embodiments of the present application, there is provided a method for supporting handover, comprising: receiving a handover request message from a source base station or from a core network; sending a source quality of service (QoS) flow to data radio bearer (DRB) mapping to a base station central unit user plane entity, wherein the base station central unit user plane entity uses the received source QoS flow to DRB mapping to process forwarded data received from the source base station; and sending a target QoS flow to DRB mapping to the base station central unit user plane entity, wherein the base station central unit user plane uses the newly received QoS flow to DRB mapping to process new data received from the core network and send to a user equipment (UE).

[0054] In one example, sending the source QoS flow to DRB mapping to the target base station central unit user plane entity comprises including to-be-established QoS flow information in to-be-established DRB information sent by a target base station central unit control plane entity to the target base station central unit user plane entity, the to-be-established QoS flow information included in the to-be-established DRB information being set according to the source QoS flow to DRB mapping; and wherein sending the target QoS flow to DRB mapping to the base station central unit user plane entity comprises including to-be-established QoS flow information in to-be-established DRB information sent by the target base station central unit control plane entity to the target base station central unit user plane entity, the to-be-established QoS flow information included in the to-be-established DRB information being set according to the target QoS flow to DRB mapping.

[0055] According to another aspect of the embodiments of the present application, there is provided a method for supporting handover, comprising: receiving a source quality of service (QoS) flow to data radio bearer (DRB) mapping from a target base station central unit control plane entity; using the received source QoS flow to DRB mapping to process forwarded data received from a source base station; receiving a target QoS flow to DRB mapping from the target base station central unit control plane entity; and using the newly received QoS flow to DRB mapping to process new data received from a core network and send to a user equipment (UE).

[0056] In one example, the mapping of source Quality of Service (QoS) flows to Data Radio Bearers (DRBs) received from the destination base station central unit control plane entity comprises including the QoS flow information to be established in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity, the QoS flow information to be established included in the DRB information to be established is set according to the mapping of the source QoS flows to DRBs; and wherein the mapping of destination QoS flows to DRBs received from the destination base station central unit control plane entity comprises including the QoS flow information to be established in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity, the QoS flow information to be established included in the DRB information to be established is set according to the mapping of the destination QoS flows to DRBs.

[0057] According to another aspect of embodiments of the present application, there is provided a method for supporting handover, comprising: receiving, by a destination base station central unit control plane entity, a handover request message from a source base station or a core network; sending, by the destination base station central unit control plane entity, a mapping of source Quality of Service (QoS) flows to Data Radio Bearers (DRBs) to a destination base station central unit user plane entity; processing, by the destination base station central unit user plane entity, forwarded data received from the source base station using the received mapping of source QoS flows to DRBs; sending, by the destination base station central unit control plane entity, a mapping of destination QoS flows to DRBs to the destination base station central unit user plane entity and sending an indication message; and processing, by the destination base station central unit user plane entity, the forwarded data received from the source base station using the received mapping of source QoS flows to DRBs and processing new data received from the core network using the newly received mapping of destination QoS flows to DRBs.

[0058] In one example, the destination base station central unit user plane entity does not delete the old mapping relationship of the source and / or does not delete the DRBs temporarily used for processing the forwarded data but not used by the destination according to the received indication message.

[0059] According to an aspect of embodiments of the present application, there is provided a method for supporting handover, comprising: receiving, by a source base station central unit control plane entity, a handover command message; and sending, by the source base station central unit control plane entity, a bearer context modification request message to a source base station central unit user plane entity, wherein the source base station central unit user plane entity forwards data according to information in the received bearer context modification request message.

[0060] In one example, the handover command message contains evolved radio access bearer (E-RAB) identification information and data forwarding tunnel information for data forwarding.

[0061] In one example, the bearer context modification request message contains data forwarding information for handover to an evolved universal terrestrial radio access network (E-UTRAN) or inter-system handover data forwarding information to inform a source base station central unit user plane entity of the data forwarding information.

[0062] In one example, the data forwarding information contains downlink data forwarding information containing a transport layer address and tunnel identification, which are data forwarding tunnel information for each E-RAB assigned by a target base station to a source base station central unit control plane entity in a handover command message.

[0063] In one example, the downlink data forwarding information further contains at least one of the following: a quality of service (Qos) flow list for forwarding data through the data forwarding tunnel; data radio bearer (DRB) identification; and E-RAB identification.

[0064] In one example, for inter-system handover, the DRB identification corresponds to and is identical to or one-to-one corresponding to the E-RAB identification.

[0065] In one example, the source base station central unit user plane entity determines inter-system handover according to the data forwarding information for handover to an E-UTRAN or inter-system handover data forwarding information and does not contain a service data adaptation protocol (SDAP) header in the forwarded data packet; or for intra-system handover, the source base station central unit user plane entity contains an SDAP header in the data packet forwarded on a tunnel corresponding to each DRB.

[0066] In one example, the source base station central unit user plane entity is informed of data forwarding tunnel information and quality of service (Qos) flow information forwarded on each tunnel through data radio bearer (DRB) information to be established and / or DRB information to be modified in the bearer context modification request message.

[0067] In one example, the bearer context modification request message contains indication information of inter-system handover, and the indication information of inter-system handover can be contained in at least one of protocol data unit (PDU) session resource modification information, DRB information to be modified, or DRB information to be established.

[0068] In one example, when a DRB of a source base station central unit user plane entity is configured in a PDU session establishment procedure, the source base station central unit control plane entity sends a transport layer address and a tunnel identifier allocated by a target base station through DRB data forwarding information in a DRB modification item, and sends a quality of service (QoS) flow that forwards data on a tunnel corresponding to the DRB through flow mapping information in the DRB modification item, wherein the DRB modification item contains a DRB identifier.

[0069] In one example, when a DRB of a source base station central unit user plane entity is not configured in a PDU session establishment procedure, the source base station central unit control plane entity sends a transport layer address and a tunnel identifier allocated by a target base station to the source base station central unit user plane entity through DRB data forwarding information added in a DRB establishment item, and sends a QoS flow that forwards data on a tunnel corresponding to the DRB to the source base station central unit user plane entity through QoS flow information to be established in the DRB establishment item, wherein the DRB establishment item contains a DRB identifier.

[0070] In one example, the source base station central unit user plane entity knows a quality of service (QoS) flow that is forwarded through the tunnel according to DRB data forwarding information and flow mapping information of each DRB in received DRB information to be modified, or the source base station central unit user plane entity knows a QoS flow that is forwarded through the tunnel according to DRB data forwarding information and QoS flow information to be established of each DRB in received DRB information to be established.

[0071] In one example, the source base station central unit user plane entity determines an inter-system handover according to received indication information of the inter-system handover, and does not include a service data adaptation protocol (SDAP) header in a forwarded data packet, and for an intra-system handover, the source base station central unit user plane entity includes the SDAP header in a data packet forwarded on a tunnel corresponding to each DRB.

[0072] According to an aspect of an embodiment of the present application, a method for supporting handover is provided, including: a source base station central unit user plane entity receiving a bearer context modification request message from a source base station central unit control plane entity; and the source base station central unit user plane entity forwarding data according to information in the received bearer context modification request message.

[0073] In one example, the bearer context modification request message contains data forwarding information for handover to an evolved universal terrestrial radio access network (E-UTRAN) or inter-system handover data forwarding information, to inform the source base station central unit user plane entity of the data forwarding information.

[0074] In one example, the data forwarding information comprises downlink data forwarding information, the downlink data forwarding information comprises transport layer address and tunnel identifier, the transport layer address and tunnel identifier are data forwarding tunnel information of each evolved radio access bearer (E-RAB) allocated by the target base station and received by the source base station central unit control plane entity in the handover command message.

[0075] In one example, the downlink data forwarding information further comprises at least one of the following: a quality of service (Qos) flow list of services forwarding data through the data forwarding tunnel; data radio bearer (DRB) identifier; and E-RAB identifier.

[0076] In one example, for inter-system handover, the DRB identifier corresponds to each E-RAB identifier and is the same as or one-to-one corresponding to the E-RAB identifier.

[0077] In one example, the source base station central unit user plane entity determines inter-system handover according to the data forwarding information for handover to E-UTRAN or inter-system handover data forwarding information, and does not include service data adaptation protocol (SDAP) packet header in the forwarded data packet; or for intra-system handover, the source base station central unit user plane entity includes the SDAP packet header in the data packet forwarded on the tunnel corresponding to each DRB.

[0078] In one example, the data forwarding tunnel information and quality of service (Qos) flow information forwarded on each tunnel are notified to the source base station central unit user plane entity through data radio bearer (DRB) information to be established and / or DRB information to be modified in the bearer context modification request message; and the source base station central unit user plane entity forwards data according to the information received in the bearer context modification request message.

[0079] In one example, the bearer context modification request message comprises indication information of inter-system handover, and the indication information of inter-system handover can be included in at least one of protocol data unit (PDU) session resource modification information, DRB information to be modified, or DRB information to be established.

[0080] In one example, when configuring the data radio bearer (DRB) of the source base station central unit user plane entity in the PDU session establishment process, the source base station central unit control plane entity sends the transport layer address and tunnel identifier allocated by the target base station through the DRB data forwarding information in the DRB modification item, and sends the quality of service (Qos) flow forwarding data on the tunnel corresponding to the DRB through the flow mapping information in the DRB modification item, wherein the DRB identifier is included in the DRB modification item.

[0081] In one example, when no DRB of the source base station central unit user plane entity is configured in the PDU session establishment procedure, the source base station central unit control plane entity sends the transport layer address and tunnel identifier allocated by the target base station to the source base station central unit user plane entity by adding DRB data forwarding information in the DRB setup item, and sends the Qos flow to be established in the tunnel corresponding to the DRB to the source base station central unit user plane entity by the Qos flow information to be established in the DRB setup item, wherein the DRB identifier is contained in the DRB setup item.

[0082] In one example, the source base station central unit user plane entity knows the quality of service Qos flow to be forwarded through the tunnel according to the DRB data forwarding information and flow mapping information of each DRB in the received DRB information to be modified, or the source base station central unit user plane entity knows the Qos flow to be forwarded through the tunnel according to the DRB data forwarding information and Qos flow information to be established of each DRB in the received DRB information to be established.

[0083] In one example, the source base station central unit user plane entity determines the inter-system handover according to the received indication information of the inter-system handover, and does not contain the service data adaptation protocol SDAP header in the forwarded data packet, and for the intra-system handover, the source base station central unit user plane entity contains the SDAP header in the data packet forwarded on the tunnel corresponding to each DRB.

[0084] According to an aspect of an embodiment of the present application, a method for supporting handover is provided, comprising: receiving a message from a target base station central unit control plane entity; receiving a data packet from a source base station; and discarding the PDCP SN contained in the received data packet according to the indication of the message.

[0085] In one example, discarding the PDCP SN contained in the received data packet includes that the target base station central unit user plane entity does not send the PDCP SN received from the source base station to the UE.

[0086] In one example, after the target base station central unit user plane entity removes the PDCP SN in the PDCP SDU, the data packet is sent to the UE through the processing of the target end.

[0087] In one example, the message can indicate discarding the PDCP SN contained in the received data packet by a display indication method or an implicit indication method.

[0088] In one example, the display indication can include containing indication information in the message, and the implicit indication can include not containing PDCP SN status information in the message.

[0089] In one example, the indication information indicates at least one of: a full configuration or a differential configuration; whether PDCP SNs are preserved; whether PDCP SNs are restarted; a packet containing a PDCP sequence number (SN) SDU is discarded; or a PDCP SN contained in a received packet is discarded.

[0090] In one example, discarding the PDCP SN contained in the received packet according to the indication of the message includes discarding the PDCP SN contained in the received packet when the indication information indicates at least one of: a full configuration; PDCP SNs are not preserved; PDCP SNs are restarted; and a PDCP SDU containing a PDCP SN is discarded or a PDCP SN contained in a received packet is discarded.

[0091] In one example, discarding the PDCP SN contained in the received packet according to the indication of the message includes discarding the PDCP SN contained in the received packet when the indication of the message includes at least one of: PDCP SN status information is not received; PDCP SN status information for a data radio bearer (DRB) is not received; a bearer context modification request message is not received; and PDCP SN status information for the DRB is not contained in the received bearer context modification request message.

[0092] According to another aspect of embodiments of the present application, there is provided a method of supporting handover, comprising: receiving a handover request message; receiving a sequence number (SN) status transfer message or a downlink radio access network (RAN) status transfer message; and sending a message to a destination base station central unit user plane entity, wherein the destination base station central unit user plane entity discards a PDCP sequence number (SN) contained in a received packet according to an indication of the message.

[0093] According to another aspect of embodiments of the present application, there is provided a method of supporting handover, comprising: a destination base station central unit user plane entity receiving indication information sent by a destination base station central unit control plane entity; the destination base station central unit user plane entity receiving a packet forwarded from a source base station or a source base station through a core network; and upon receiving the indication information from the destination base station central unit control plane entity, the destination base station central unit user plane entity discarding a PDCP SN contained in the received packet.

[0094] In one example, if the indication information indicates full configuration or PDCP SN not preserved or PDCP restart or indicates discard PDCP SDUs containing PDCP SN information or indicates discard PDCP SN information, the destination base station central unit user plane entity discards PDCP SN contained in the received data packet.

[0095] According to another aspect of embodiments of the present application, there is provided a method for supporting handover, comprising: a destination base station central unit user plane entity receiving a message sent by a destination base station central unit control plane entity; the destination base station central unit user plane entity receiving data packets forwarded from a source base station or a source base station through a core network; and if no PDCP SN status information is received, the destination base station central unit user plane entity discarding PDCP SN contained in the received data packet. Figure 7 New solution

[0096] According to another aspect of embodiments of the present application, there is provided a method for supporting handover, comprising: a destination base station receiving a handover request message; the destination base station sending information about full configuration or differential configuration to a source base station; and the source base station forwarding data packets not containing PDCP SN to the destination base station based on the information.

[0097] In one example, the information about full configuration or differential configuration can be at least one of the following: information about whether PDCP SN status is preserved, information about whether PDCP SN is restarted, information about not needing PDCP SN, or information about not needing data packets containing PDCP SN.

[0098] In one example, if the source base station supports a user plane and control plane separation architecture, the source base station central unit control plane entity can inform the source base station central unit user plane entity that data packets not containing PDCP SN are forwarded by an explicit indication manner or an implicit indication manner.

[0099] In one example, the indication information can indicate at least one of the following: full configuration or differential configuration; whether PDCP SN status is preserved; whether only new data is sent; whether PDCP SDUs containing PDCP SN are sent; whether PDCP data packets sent to a user equipment (UE) without being acknowledged by the UE are sent; whether data packets containing PDCP SN are forwarded; and whether only PDCP SDUs not containing PDCP SN are sent.

[0100] According to another aspect of the embodiments of the present application, a method for supporting handover is provided, including: receiving a handover request message by a target base station or a target base station central unit control plane entity; sending information of full configuration or Delta configuration to a source base station or a source base station central unit control plane entity by the target base station or the target base station central unit control plane entity; and forwarding data packets without PDCP SN to a target base station by the source base station.

[0101] According to another aspect of the embodiments of the present application, a method for supporting handover is provided, including: receiving a handover related message; and indicating information for data forwarding to a source base station central unit user plane entity, wherein the source base station central unit user plane entity forwards PDCP SDUs without PDCP SN to a target base station based on the information for data forwarding.

[0102] In one example, the source base station central unit control plane entity can indicate the information for data forwarding to the source base station central unit user plane entity by an explicit indication method or an implicit indication method.

[0103] In one example, the source base station central unit user plane entity forwards PDCP SDUs without PDCP SN to the target base station when at least one of the following is determined according to the indication information: PDCP SN status is not reserved; only new data is sent; PDCP SDUs with PDCP SN are not sent; PDCP data packets sent to a user equipment (UE) without acknowledgement by the UE are not forwarded; and only PDCP SDUs without PDCP SN are sent.

[0104] In one example, for a DRB requested to be modified or established by the source base station central unit control plane entity, if the source base station central unit control plane entity does not request PDCP SN status information, the source base station central unit user plane entity forwards PDCP SDUs without PDCP SN to the target base station.

[0105] According to another aspect of the embodiments of the present application, a method for supporting handover is provided, including: receiving a handover command message or a handover request acknowledgement message by a source base station central unit control plane entity; indicating information for data forwarding to a source base station central unit user plane entity by the source base station central unit control plane entity in an explicit manner or an implicit manner; and forwarding data packets without PDCP SN to a target base station by the source base station central unit user plane entity.

[0106] According to another aspect of the embodiments of the present application, a method for supporting handover is provided, including: receiving indication information for data forwarding; and not sending PDCP service data units (SDUs) with packet data convergence protocol (PDCP) SN to a target base station based on the indication information for data forwarding.

[0107] In an example, the information indicating data forwarding can be received by an explicit indication method or an implicit indication method.

[0108] In an example, the source base station central unit user plane entity forwards PDCP SDUs without PDCP SN to the target base station when at least one of the following is determined according to the indication information: PDCP SN status is not preserved; only new data is sent; PDCP SDUs containing PDCP SN are not sent; PDCP data packets sent to a user equipment (UE) that are not acknowledged by the UE are not sent; PDCP SN is not sent; and only PDCP SDUs without PDCP SN are sent.

[0109] In an example, the source base station central unit user plane entity knows that PDCP SN is not preserved or the source base station central unit control plane entity does not send PDCP SN status information to the target base station by not requesting PDCP SN status information, and forwards PDCP SDUs without PDCP SN to the target base station.

[0110] According to another aspect of embodiments of the present application, a method for supporting handover is provided, comprising: receiving, by a source base station central unit user plane entity, information for data forwarding and channel information for data forwarding sent by a source base station central unit control plane entity; and forwarding, by the source base station central unit control plane entity, data packets without PDCP SN to a target base station.

[0111] According to another aspect of embodiments of the present application, an apparatus for supporting handover is provided, comprising: a transceiver that transmits and receives signals; a processor; and a memory that stores instructions executable by the processor, which when executed by the processor, cause the processor to perform any of the methods described above.

[0112] Technical effects

[0113] According to embodiments of the present application, the problem of coordination between a source base station and a target base station during a handover process can be solved. In particular, in the case where the source base station and / or the target base station support control plane and data plane separation, the source base station central unit control plane entity, the source base station central unit user plane entity, the target base station central unit control plane entity, and / or the target base station central unit user plane entity can be ensured to work in full coordination.

[0114] In addition, the method and apparatus for supporting handover according to embodiments of the present application can also reduce data loss, reduce data interruption time, avoid sending useless data packets over the air, improve the efficiency of data forwarding, and ensure service continuity. BRIEF DESCRIPTION OF DRAWINGS

[0115] The present application will become more readily appreciated when considered in connection with the following detailed description and, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements in which:

[0116] Figure 1 is an exemplary system architecture of System Architecture Evolution (SAE);

[0117] Figure 2 is an exemplary system architecture according to various embodiments of the present disclosure;

[0118] Figure 3 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0119] Figure 4 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0120] Figure 5 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0121] Figure 6 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0122] Figure 7 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0123] Figure 8 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0124] Figure 9 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0125] Figure 10 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0126] Figure 11 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0127] Figure 12 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0128] Figure 13 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0129] Figure 14 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0130] Figure 15 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0131] Figure 16 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0132] Figure 17 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0133] Figure 18 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0134] Figure 19 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0135] Figure 20 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0136] Figure 21 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0137] Figure 22 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0138] Figure 23 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0139] Figure 24 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0140] Figure 25 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0141] Figure 26 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0142] Figure 27 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0143] Figure 28 is an exemplary flowchart illustrating a method for supporting handover according to an embodiment of the present application;

[0144] Figure 29An exemplary flow diagram illustrating a method for supporting handover according to an embodiment of the application is shown; and

[0145] Figure 30 An exemplary block diagram illustrating an apparatus for supporting handover according to an embodiment of the application is shown. DETAILED DESCRIPTION

[0146] The following discussion Figures 1 to 8 The principles of the disclosure described in this patent document can be implemented in any of a variety of systems or devices. One or more aspects of the disclosure can be implemented in a system architecture such as the exemplary system architecture 100 shown in FIG. 1.

[0147] Figure 1 is an exemplary system architecture 100 of System Architecture Evolution (SAE). User Equipment (UE) 101 is a terminal device used to receive data. Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 102 is a radio access network that includes macro base stations (eNodeB / NodeB) that provide a radio network interface for UEs to access the wireless network. Mobile Management Entity (MME) 103 is responsible for managing the mobility context, session context, and security information of the UE. Serving Gateway (SGW) 104 provides mainly user plane functions, and MME 103 and SGW 104 can be in the same physical entity. Packet Data Network Gateway (PGW) 105 is responsible for charging, lawful interception, etc., and can also be in the same physical entity as SGW 104. Policy and Charging Rules Function (PCRF) 106 provides Quality of Service (QoS) policy and charging rules. Serving General Packet Radio Service (GPRS) Support Node (SGSN) 108 is a network node device in Universal Mobile Telecommunications System (UMTS) that provides routing for data transmission. Home Subscriber Server (HSS) 109 is a home subscriber subsystem of the UE that is responsible for protecting user information including the current location of the user equipment, address of the serving node, user security information, packet data context of the user equipment, etc.

[0148] Figure 2 is an exemplary system architecture 200 according to various embodiments of the disclosure. Other embodiments of system architecture 200 can be used without departing from the scope of the disclosure.

[0149] A user equipment (UE) 201 is a terminal device used to receive data. A next generation radio access network (NG-RAN) 202 is a radio access network including a base station (gNB or eNB connected to a 5G core network 5GC, eNB connected to the 5GC is also called ng-gNB) that provides a radio network interface for the UE to access. An access control and mobility management function entity (AMF) 203 is responsible for managing the mobility context of the UE and security information. A user plane function entity (UPF) 204 mainly provides the function of the user plane. A session management function entity SMF 205 is responsible for session management. A data network (DN) 206 includes services such as operator services, access to the Internet, and third-party services. The base station can be divided into a base station central unit and a base station distribution unit. The base station central unit can be divided into a base station central unit control plane entity and a base station central unit user plane entity. Or the base station can be divided into a base station control plane entity and a base station user plane entity.

[0150] Exemplary embodiments of the present disclosure are further described below with reference to the accompanying drawings.

[0151] The text and drawings are provided only as examples to help understand the present disclosure. They should not be interpreted as limiting the scope of the present disclosure in any way. Although certain embodiments and examples have been provided, it will be apparent to those skilled in the art based on the disclosure herein that modifications can be made to the embodiments and examples shown without departing from the scope of the present disclosure.

[0152] The base station central unit control plane entity in the embodiments of the present disclosure can also be referred to as a base station control plane entity, which refers to a logical entity containing a radio resource control (RRC) and a packet data convergence protocol (PDCP) control plane part in a base station.

[0153] The base station central unit user plane entity in the embodiments of the present disclosure can also be referred to as a base station user plane entity, which refers to a logical entity containing a packet data convergence protocol (PDCP) user plane function part in a base station. The logical entity can also contain a service data adaptation protocol (SDAP) function.

[0154] In the process of handover, the source base station can send the UE configuration information at the source base station end to the target base station, and the target base station decides whether to use full configuration or delta configuration. The source base station does not know whether the target base station decides to use full configuration or delta configuration. For the data radio bearers (DRBs) accepted by the target base station for downlink data forwarding, the source base station forwards the data packets sent to the UE but not acknowledged by the UE and fresh data packets to the target base station. In the case where the target base station is a control plane and user plane separated architecture, the target base station central unit control plane entity decides whether to use full configuration or delta configuration, and the target base station central unit user plane entity does not know whether full configuration or delta configuration is used for handover. The target base station central unit user plane entity will send all the forwarded data packets received from the source base station to the UE. For full configuration, the PDCP sequence number (SN) state is not saved, and the target base station central unit user plane entity sends the data packets sent to the UE but not acknowledged by the UE forwarded by the source base station to the UE, which is useless or the SN contained in the data packets forwarded by the source base station is useless, wasting air interface resources and affecting the data re-ordering problem at the UE end. The present application provides two ways to solve this problem. Including:

[0155] Method one: the target base station central unit control plane entity sends indication information to the target base station central unit user plane entity, so that the target base station central unit user plane entity sends appropriate data to the UE according to the indication information. As described in the method of Figures 3 to 8 .

[0156] Method two: the target base station receives the handover request message, and the target base station sends information of full configuration or delta configuration or whether to save the PDCP SN state to the source base station, and the source base station forwards data to the target base station according to the received information. In the case where the source base station is a control plane and user plane separated architecture, the source base station central unit control plane entity sends indication information to the source base station central unit user plane entity, and the source base station central unit user plane entity forwards data to the target base station according to the received information. As described in the method of Figures 9 to 14 .

[0157] In the handover procedure, the source base station can send the UE configuration information at the source base station side to the target base station, which contains the DRB configuration information at the source base station. The configuration information can also contain the mapping of Quality of Service (Qos) flows to DRBs. The target base station decides whether to use the same DRB configuration as the source base station and / or the same mapping of Qos flows to DRBs. If the target base station decides to use different DRB configuration and / or different mapping of Qos flows to DRBs than the source base station, in order to ensure lossless data during the handover procedure, the target base station can also temporarily configure the old DRB and / or the same mapping of Qos flows to DRBs as the source base station for processing the data forwarded by the source base station. For the new data received from the core network, the target base station uses the new DRB and / or the mapping of Qos flows to DRBs decided by the target base station. In the case that the target base station is a split architecture of control plane and user plane, the target base station central unit control plane entity decides the DRB configuration and the mapping of Qos flows to DRBs. The target base station central unit control plane entity sends a message to the target base station central unit user plane entity, which contains the DRBs to be established or modified and the Qos flows mapped on the DRBs. The current mechanism is that the target base station central unit user plane entity only receives a set of mapping information of Qos flows to DRBs, and the target base station central unit user plane entity does not know whether the mapping information is the new mapping decided by the target end or the mapping of the source end. The target base station central unit user plane entity receives the data forwarded from the source base station and the new data received from the core network, and in the above scenario, the target base station central unit user plane entity uses the received information of Qos flows mapped on the DRBs to process the forwarded data from the source base station and the new data received from the core network, which can cause the problem of data loss or not using the target end Qos flow to DRB mapping to process the new data received from the core network. The present application Figure 15 、 Figure 18 、 Figure 21 and Figure 24 provides four methods to solve this problem. Figure 25 The method of releasing the old DRB configured on the base station distribution unit (gNB-DU) in these methods is given.

[0158] For UE handover from 5G system (5GS) to evolved packet system (EPS), the source NG-RAN node decides the mapping of Qos flow to DRB at PDU session establishment, the source base station central unit control plane entity sends the information of DRB to be established and the information of Qos flow mapped on the DRB to the source base station central unit user plane entity, and the source base station central unit user plane entity processes the data received from the core network according to the mapping. For direct data forwarding from the source NG-RAN to the target base station, a tunnel for each E-RAB (Evolved Radio Access Bearer) is established between the source NG-RAN node and the target base station for data forwarding. The target base station allocates a tunnel for each E-RAB and sends it to the source NG-RAN node. The E-RAB for Qos flow mapping is determined by the core network. If the number of E-RABs for Qos flow mapping is more than the number of DRBs decided by the NG-RAN, the source base station central unit control plane entity cannot send the tunnel information corresponding to each E-RAB to the source base station central unit user plane entity through the existing bearer context modification request message.

[0159] In addition, for inter-system handover from 5GS to EPS, the data packet header forwarded by the source base station does not contain the SDAP header, while for intra-system handover of 5GS, the data forwarded on the DRB tunnel can contain the SDAP header. The data forwarding is performed by the source base station central unit user plane entity forwarding data to the target base station. In the prior art, the source base station central unit user plane entity does not know when to include the SDAP header and when not to include the SDAP header in the forwarded data packet. Figures 24 to 25 Two methods are given to solve the above problems.

[0160] Figure 3 FIG. 3 is a flowchart illustrating an example of a method 300 for supporting handover according to an embodiment of the present application. The method 300 can be used for intra-system handover or inter-system handover, and can be performed at the target base station central unit user plane entity side.

[0161] As shown in FIG. 3, in the method 300, at step S301, a message is received from a target base station central unit control plane entity. Figure 3

[0162] At step S302, a data packet is received from a source base station.

[0163] At step S303, according to an indication of the message, a PDCP service data unit (SDU) containing a PDCP sequence number (SN) in the received data packet is discarded.

[0164] ​Alternatively, in step S303, the PDCP SN contained in the received data packet is discarded according to the indication of the message. Discarding the PDCP SN contained in the received data packet means that the destination base station central unit user plane entity does not send the PDCP SN received from the source base station to the UE. The data packet can be sent to the UE after the destination base station central unit user plane entity removes the PDCP SN in the PDCP SDU through the processing at the destination.

[0165] According to an embodiment of the present application, the message can indicate discarding the PDCP SDU containing the PDCP SN in the received data packet or discarding the PDCP SN contained in the received data packet by explicit indication method or implicit indication method. The explicit indication can include indication information in the message, and the implicit indication can include no PDCP SN status information in the message.

[0166] Specifically, in one example of the explicit indication method, the message received from the destination base station central unit control plane entity in step S301 includes indication information. The indication information can indicate at least one of the following: full configuration or delta configuration; whether the PDCP SN is reserved; whether the PDCP SN is restarted; discarding the data packet containing the PDCP sequence number (SN) of the PDCP service data unit (SDU) or discarding the PDCP SN contained in the received data packet. The PDCP restart means that the PDCP is deleted and then added again.

[0167] The indication information can be sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity through a bearer context modification request message. The bearer context modification request message is used for bearer establishment or bearer modification.

[0168] The destination base station central unit user plane entity saves the received information.

[0169] In one example, in step S302, the destination base station central unit user plane entity receives the data packet from the source base station or forwarded by the source base station through the core network. If the source base station also supports the architecture of separation of user plane and control plane, the data is received from the source base station central unit user plane entity.

[0170] In one example, at step S303, the destination base station central unit user plane entity discards PDCP SDUs containing PDCP SNs or discards PDCP SNs contained in received data packets when the indication information indicates at least one of the following: full configuration; PDCP SNs are not preserved; PDCP re-start; and discard PDCP SDUs containing PDCP SNs or discard PDCP SNs contained in received data packets.

[0171] That is, the destination base station central unit user plane entity discards PDCP SDUs containing PDCP SNs that the source base station attempts to send to a user equipment (UE). The destination base station central unit user plane entity identifies these data packets and discards them based on the presence of SNs in the forwarded general packet radio service (GPRS) tunneling protocol (GTP) user plane (GTP-U) data packets. Or the destination base station central unit user plane entity discards PDCP SNs in PDCP SDUs received from the source base station.

[0172] On the other hand, in one example of the implicit indication method, at step S303, the destination base station central unit user plane entity discards PDCP SDUs containing PDCP SNs or discards PDCP SNs contained in received data packets when the indication of the message includes at least one of the following: no PDCP SN status information is received; no PDCP SN status information for a data radio bearer (DRB) is received; no bearer context modification request message is received; and no PDCP SN status information for a DRB is contained in the received bearer context modification request message.

[0173] Specifically, if the destination base station central unit user plane entity does not receive PDCP SN status information in step S301, the destination base station central unit user plane entity discards received PDCP SDUs containing PDCP SNs forwarded from the source base station that are not sent to the UE. Or, if the destination base station central unit user plane entity does not receive PDCP SN status information for a data radio bearer (DRB) in step S301, the destination base station central unit user plane entity discards received PDCP SDUs containing PDCP SNs forwarded from the source base station that are not sent to the UE.

[0174] That is, the destination base station central unit user plane entity discards PDCP SDUs containing PDCP SNs that the source base station attempts to send to a user equipment (UE), the destination base station central unit user plane entity identifies these data packets and discards them based on the presence of SNs in the forwarded GTP-U data packets.

[0175] Alternatively, if the target base station central unit user plane entity does not receive the bearer context modification request message, the target base station central unit user plane entity discards the received PDCP SNs contained in the PDCP SDUs forwarded from the source base station. Or, if the target base station central unit user plane entity receives the bearer context modification request message without PDCP SN status information for a certain DRB, the target base station central unit user plane entity discards the received PDCP SNs contained in the PDCP SDUs for the DRB forwarded from the source base station.

[0176] In particular, in the example of discarding the PDCP SNs contained in the received data packets, if the target base station central unit user plane entity does not receive the PDCP SN status information in step S301, the target base station central unit user plane entity discards the PDCP SNs contained in the received data packets, and the PDCP SNs received from the source base station are not transmitted to the UE. Or, if the target base station central unit user plane entity does not receive the PDCP SN status information for a data radio bearer (DRB) in step S301, the target base station central unit user plane entity discards the PDCP SNs contained in the received data packets, and the PDCP SNs received from the source base station are not transmitted to the UE.

[0177] Alternatively, if the target base station central unit user plane entity does not receive the bearer context modification request message, the target base station central unit user plane entity discards the PDCP SNs contained in the received data packets, and the PDCP SNs received from the source base station are not transmitted to the UE. Or, if the target base station central unit user plane entity receives the bearer context modification request message without PDCP SN status information for a certain DRB, the target base station central unit user plane entity discards the PDCP SNs contained in the received data packets, and the PDCP SNs received from the source base station are not transmitted to the UE.

[0178] The target base station central unit user plane entity adds the PDCP SNs to the PDCP SDUs from which the PDCP SNs are removed, and transmits the PDCP SDUs to the UE after processing through the PDCP layer and other layers.

[0179] Thereafter, the target base station central unit user plane entity adds the PDCP SNs to the received PDCP SDUs without PDCP SNs, and transmits the PDCP SDUs to the UE after processing through the PDCP layer and other layers.

[0180] The PDCP SDUs without PDCP SNs can be fresh data.

[0181] According to the embodiment of the present application, the target base station central unit user plane entity can discard data not needed to be sent to the UE or PDCP SNs not needed to be sent to the UE, and only send the needed data to the UE, thereby improving the efficiency of data transmission and avoiding wasting air interface resources.

[0182] Figure 4 FIG. 4 is a flowchart illustrating an example of a method 400 for supporting handover according to an embodiment of the present application. The method 400 can be used for intra-system handover or inter-system handover, and can be performed at a target base station central unit control plane entity.

[0183] As shown in FIG. 4, in the method 400, at step S401, a handover request message is received. Figure 4

[0184] At step S402, a sequence number SN status transfer message or a downlink radio access network RAN status transfer message is received.

[0185] At step S403, a message is sent to a target base station central unit user plane entity, wherein the target base station central unit user plane entity discards, according to an indication of the message, a packet data convergence protocol PDCP service data unit SDU containing a PDCP sequence number SN in a received data packet.

[0186] Alternatively, at step S403, a message is sent to a target base station central unit user plane entity, wherein the target base station central unit user plane entity discards, according to an indication of the message, a PDCP SN contained in a received data packet.

[0187] In one example, at step S401, the target base station central unit control plane entity can receive a handover request message. The handover request message can be received from a source base station or a source base station central unit control plane entity or received from a core network. The handover request message received from the source base station or the source base station central unit control plane entity is an Xn application protocol (AP) message or other inter-base station message. And the handover request message received from the core network is a next generation application protocol (NGAP) message or other inter-base station and core network message.

[0188] The handover request message received from the core network contains a handover type, which can include intra-system handover or inter-system handover.

[0189] In addition, the handover request message received from the source base station or the source base station central unit control plane entity indicates by default that the handover type is intra-system handover.

[0190] Whether to use full configuration or differential configuration can be determined by the target base station central unit control plane entity.

[0191] ​In one example, at step S402, the destination base station central unit control plane entity receives the SN status transfer message or the downlink RAN status transfer message. The SN status transfer message can be received from the source base station or the source base station central unit control plane entity. The SN status transfer message received from the source base station or the source base station central unit control plane entity can be an Xn application protocol (AP) message or other inter-base station message. The downlink RAN status transfer message can be received from the core network.

[0192] As mentioned before, at step S403, the indication of discarding the PDCP SDU containing the PDCP SN in the received data packet or discarding the PDCP SN contained in the received data packet can be indicated by explicit indication method or implicit indication method. The explicit indication can include containing the indication information in the message, and the implicit indication can include not containing the PDCP SN status information in the message.

[0193] The indication information can be sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity through the bearer context modification request message. The bearer context modification request message is used for bearer establishment or bearer modification.

[0194] For the implicit indication, the destination base station central unit control plane entity can decide whether to contain the PDCP SN status information in the bearer context modification request message sent to the destination base station central unit user plane entity for each DRB to be modified or established. The destination base station central unit control plane entity does not contain the PDCP SN status information in the bearer context modification request message sent to the destination base station central unit user plane entity for a DRB when deciding to use full configuration for the DRB.

[0195] The explicit indication method or the implicit indication method is similar to the method 300 described above with reference to Figure 3 The description of the method 300 is not repeated here.

[0196] The destination base station central unit control plane entity sends the indication information to the destination base station central unit user plane entity when the handover is inter-system handover. The destination base station central unit control plane entity knows whether it is inter-system handover according to the handover type contained in the received handover request message.

[0197] It should be noted that the handover preparation message for inter-system handover is sent through the core network, so for inter-system handover, the handover request message can only be received from the core network.

[0198] In another example, the destination base station central unit control plane entity sends the indication information to the destination base station central unit user plane entity when deciding to use full configuration.

[0199] For intra-system handover, the destination base station central unit control plane entity decides whether to use full configuration or delta configuration. Full configuration is used for inter-system handover.

[0200] According to the embodiment of the present application, the destination base station central unit control plane entity can make the destination base station central unit user plane entity know how to process the received data forwarded from the source base station, so that the data not needed to be sent to the UE or the PDCP SN not needed to be sent to the UE can be discarded, and only the needed data is sent to the UE, thereby improving the efficiency of data forwarding and avoiding wasting air interface resources.

[0201] Figure 5 FIG. 4 is an exemplary flow chart illustrating a method 400 for supporting handover according to an embodiment of the present application. The method 500 can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0202] In step S501, the destination base station central unit user plane entity receives the indication information sent by the destination base station central unit control plane entity. The indication information can be information of full configuration or delta configuration, or information of PDCP SN reservation, or information of PDCP restart, or information indicating to discard the data packet containing PDCP sequence number (SN) of PDCP service data unit (SDU), or information indicating to discard PDCP SN. The indication information can be sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity through a bearer context modification request message. The PDCP restart refers to PDCP deletion and re-addition.

[0203] The destination base station central unit user plane entity saves the received information.

[0204] In step S502, the destination base station central unit user plane entity receives the data packet forwarded from the source base station or the source base station through the core network. If the source base station also supports the architecture of separation of user plane and control plane, the data is received from the source base station central unit user plane entity.

[0205] Step S503, the destination base station central unit user plane entity receives the indication information from the destination base station central unit control plane entity. If the indication information indicates full configuration or PDCP SN is not preserved or PDCP is restarted or indicates discard PDCP SDUs containing PDCP SN information or indicates discard PDCP SN information, the destination base station central unit user plane entity discards PDCP SDUs containing PDCP SN or discards PDCP SN contained in the received data packet. That is, the destination base station central unit user plane entity discards PDCP SDUs that the source base station attempts to send to the UE. The destination base station central unit user plane entity identifies these data packets according to the presence of SN in the forwarded general packet radio service (GPRS) tunneling protocol (GTP) user plane (GTP-U) data packets and discards them. Alternatively, the destination base station central unit user plane entity discards PDCP SN contained in the received data packet, and PDCP SN received from the source base station is not sent to the UE. The destination base station central unit user plane entity removes the PDCP SN of the PDCP SDU, processes through the PDCP layer and other layers, and sends to the UE.

[0206] The destination base station central unit user plane entity adds PDCP SN to the received PDCP SDUs without PDCP SN, processes through the PDCP layer and other layers, and sends to the UE. The PDCP SDUs without PDCP SN can be fresh data.

[0207] So far, the description of the method 500 for supporting handover according to the present application is completed. Through the method, the destination base station central unit user plane entity can discard data that does not need to be sent to the UE, improve the efficiency of data transmission, and avoid wasting air interface resources.

[0208] Figure 6 is an exemplary flow chart illustrating a method 600 for supporting handover according to an embodiment of the present application. The method 600 can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0209] Step S601, the destination base station central unit control plane entity receives a handover request message. The handover request message is received from the source base station or the source base station central unit control plane entity or received from the core network. The handover request message received from the source base station or the source base station central unit control plane entity is an Xn application protocol (AP) message or other inter-base station message. The handover request message received from the core network is an NGAP message or other message between the base station and the core network.

[0210] For the handover request message received from the core network, the handover request message contains a handover type.

[0211] The destination base station central unit control plane entity decides whether to use full configuration or differential configuration.

[0212] At step S602, the destination base station central unit control plane entity receives the SN status transfer message or the downlink RAN status transfer message. The SN status transfer message is received from the source base station or the source base station central unit control plane entity. The message received from the source base station or the source base station central unit control plane entity is an Xn application protocol (AP) message or other inter-base station message. The downlink RAN status transfer message is received from the core network. The handover request message received from the core network is an NGAP message or other message between the base station and the core network.

[0213] At step S603, the destination base station central unit control plane entity sends the indication information to the destination base station central unit user plane entity. The indication information is the same as that in step S501, which is not repeated here.

[0214] The destination base station central unit control plane entity sends the indication information to the destination base station central unit user plane entity through a bearer context modification request message.

[0215] The destination base station central unit control plane entity sends the indication information to the destination base station central unit user plane entity when the handover is an inter-system handover. The destination base station central unit control plane entity knows whether it is an inter-system handover according to the handover type contained in the received handover request message. It should be noted that the handover preparation message for the inter-system handover is sent through the core network, so for the inter-system handover, the handover request message can only be received from the core network. Alternatively, the destination base station central unit control plane entity sends the indication information to the destination base station central unit user plane entity when it decides to use full configuration. For an intra-system handover, the destination base station central unit control plane entity decides whether to use full configuration or differential configuration. Full configuration is used for the inter-system handover.

[0216] So far, the description of the method 600 for supporting handover according to the present application is completed. Through the method, the destination base station central unit control plane entity can make the destination base station central unit user plane entity know how to process the received data forwarded from the source base station, so that the data or PDCP SNs that do not need to be sent to the UE can be discarded, the efficiency of data forwarding is improved, and the waste of air interface resources is avoided.

[0217] Figure 7 is an exemplary flowchart illustrating a method 700 for supporting handover according to an embodiment of the present application. The method 700 can be used for an intra-system handover or an inter-system handover. The method includes the following steps.

[0218] Step S701, the destination base station central unit user plane entity receives the message sent by the destination base station central unit control plane entity. The message is used to carry the establishment or bearer modification. The message can be a bearer modification request message.

[0219] The destination base station central unit user plane entity saves the received information.

[0220] Step S702, the destination base station central unit user plane entity receives the data packet forwarded from the source base station or the source base station through the core network. If the source base station also supports the architecture of separating the user plane and the control plane, the data is received from the source base station central unit user plane entity.

[0221] Step S703, if the destination base station central unit user plane entity does not receive the PDCP SN status information in step S701, the destination base station central unit user plane entity discards the received PDCP SDUs containing PDCP SNs forwarded from the source base station, and the data packet is not sent to the UE. Or for the data radio bearer (DRB) for which the PDCP SN status information is not received in step S701, the destination base station central unit user plane entity discards the received PDCP SDUs containing PDCP SNs forwarded from the source base station, and the data packet is not sent to the UE. That is, the destination base station central unit user plane entity discards the PDCP SDUs that the source base station attempts to send to the UE, and the destination base station central unit user plane entity identifies these data packets and discards them according to the presence of SN in the forwarded GTP-U data packet. Or if the destination base station central unit user plane entity does not receive the PDCP SN status information, the destination base station central unit user plane entity discards the received PDCP SDUs containing PDCP SNs forwarded from the source base station. Or if the destination base station central unit user plane entity does not receive the bearer context modification request message, the destination base station central unit user plane entity discards the received PDCP SDUs containing PDCP SNs forwarded from the source base station. Or if the destination base station central unit user plane entity does not receive the PDCP SN status information of a certain DRB in the received bearer context modification request message, the destination base station central unit user plane entity discards the received PDCP SDUs containing PDCP SNs of the DRB forwarded from the source base station.

[0222] If the destination base station central unit user plane entity does not receive the PDCP SN status information in step S701, the destination base station central unit user plane entity removes the PDCP SN contained in the received data packet, and the PDCP SN received from the source base station is not sent to the UE. Or for the data radio bearers (DRBs) for which the destination base station central unit user plane entity does not receive the PDCP SN status information in step S701, the destination base station central unit user plane entity removes the PDCP SN contained in the received data packet, and the PDCP SN received from the source base station is not sent to the UE. Or for the data radio bearers (DRBs) for which the destination base station central unit user plane entity does not receive the PDCP SN status information in step S701, the destination base station central unit user plane entity removes the PDCP SN contained in the received data packet, and the PDCP SN received from the source base station is not sent to the UE. Or for the data radio bearers (DRBs) for which the destination base station central unit user plane entity does not receive the PDCP SN status information in step S701, the destination base station central unit user plane entity removes the PDCP SN contained in the received data packet, and the PDCP SN received from the source base station is not sent to the UE.

[0223] The destination base station central unit user plane entity adds PDCP SN to the PDCP SDUs without PDCP SN, processes through the PDCP layer and other layers, and sends to the UE. The PDCP SDUs without PDCP SN can be fresh data.

[0224] So far, the description of the method 700 for supporting handover according to the present application is completed. Through the method, the destination base station central unit user plane entity can discard the data or PDCP SNs that do not need to be sent to the UE, improve the efficiency of data transmission, and avoid wasting air interface resources.

[0225] Figure 8 is an exemplary flow chart illustrating a method 800 for supporting handover according to an embodiment of the present application. The method 800 can be used for intra-system handover or inter-system handover. The method comprises the following steps.

[0226] Steps S801 to S802 are the same as steps S601 to S602, and detailed technical description is omitted here.

[0227] In step S803, the destination base station central unit control plane entity decides whether to send a bearer context modification request message to the destination base station central unit user plane entity, or the destination base station central unit control plane entity decides whether to contain PDCP SN status information in the bearer context modification request message sent to the destination base station central unit user plane entity for each DRB to be modified or established.

[0228] The destination base station central unit control plane entity can not send a bearer context modification request message to the destination base station central unit user plane entity when the handover is an inter-system handover, or the destination base station central unit control plane entity does not include PDCP SN status information in the bearer context modification request message sent to the destination base station central unit user plane entity. The destination base station central unit control plane entity knows whether the handover is an inter-system handover according to the handover type included in the received handover request message. It should be noted that the handover preparation message for an inter-system handover is sent by the core network, so for an inter-system handover, the handover request message can only be received from the core network.

[0229] Alternatively, the destination base station central unit control plane entity does not send a bearer context modification request message to the destination base station central unit user plane entity when it decides to use full configuration. For an intra-system handover, the destination base station central unit control plane entity decides whether to use full configuration or differential configuration. An inter-system handover uses full configuration.

[0230] Alternatively, the destination base station central unit control plane entity does not include PDCP SN status information for a certain DRB in the bearer context modification request message sent to the destination base station central unit user plane entity when it decides to use full configuration for the DRB.

[0231] So far, the description of the method 800 for supporting handover according to the present application has been completed. Through the method, the destination base station central unit control plane entity can make the destination base station central unit user plane entity know how to process the received forwarded data, so that data that does not need to be sent to the UE or PDCP SN that does not need to be sent to the UE can be discarded, the efficiency of data forwarding is improved, and waste of air interface resources is avoided.

[0232] Figure 9 FIG. 9 is a flowchart illustrating an example of a method 900 for supporting handover according to an embodiment of the present application. The method 900 can be used for intra-system handover or inter-system handover, and can be performed between a destination base station and a source base station.

[0233] As shown in FIG. 9, in the method 900, at step S901, the destination base station receives a handover request message. Figure 9

[0234] At step S902, the destination base station sends information about full configuration or differential configuration to the source base station. The information about full configuration or differential configuration can also be information about whether to retain PDCP SN status, information about whether to restart PDCP SN, information about not needing PDCP SN, or information about not needing a data packet including PDCP SN.

[0235] ​In the present application, the information of full configuration or differential configuration can be information of whether PDCP SN status is preserved, information of whether PDCP SN is restarted, information of whether the forwarded data packet does not need PDCP SN, or information of whether the data packet does not need to contain PDCP SN. The information of full configuration or differential configuration will not be described again below.

[0236] In step S903, the source base station does not send PDCP service data unit (SDU) containing packet data convergence protocol (PDCP) sequence number (SN) to the target base station based on the information.

[0237] Alternatively, in step S903, the source base station forwards the data packet not containing PDCP SN to the target base station based on the information. The forwarded data packet can be PDCP SDU. For the data packet that has been allocated PDCP SN, the source base station also does not contain PDCP SN in the forwarded data packet.

[0238] In one example, in step S901, the target base station or the target base station central unit control plane entity receives the handover request message. The handover request message is received from the source base station or the source base station central unit control plane entity or received from the core network. The handover request message received from the source base station or the source base station central unit control plane entity is Xn application protocol (AP) message or other inter-base station message. The handover request message received from the core network is NGAP message or other inter-base station and core network message.

[0239] For the handover request message received from the core network, the handover request message contains the handover type.

[0240] The target base station or the target base station central unit control plane entity can decide whether to use full configuration or differential configuration. In addition, the target base station or the target base station central unit control plane entity can also decide whether to use full configuration or differential configuration for each established DRB.

[0241] In this example, in step S902, the target base station or the target base station central unit control plane entity can send the information of full configuration or differential configuration to the source base station or the source base station central unit control plane entity.

[0242] The target base station or the target base station central unit control plane entity can send the information to the source base station or the source base station central unit control plane entity through the interface message between the target base station and the source base station. The target base station or the target base station central unit control plane entity can also send the information to the source base station or the source base station central unit control plane entity through the core network, for example, sending the information of full configuration or differential configuration to the source base station or the source base station central unit control plane entity through the target-to-source transparent transmitter. The full configuration or differential configuration can be for each DRB.

[0243] In one example, for handover preparation is performed directly between base stations (e.g. Xn handover), the target base station can send the information of full configuration or differential configuration to the source base station or source base station central unit control plane entity through the handover request acknowledge message.

[0244] In one example, for handover preparation is performed through core network (e.g. NG handover), the target base station can send the information of full configuration or differential configuration through the handover request acknowledge from target base station to core network and the handover command message from core network to source base station. Here, the description of the interaction between core network entities is omitted in order to avoid obscuring the subject matter of the present application.

[0245] In one example, in step S903, the source base station receives the information in step S902. Based on the information, the source base station does not forward the data packet containing PDCP SN to the target base station. For the PDCP data packet that the source base station sends to the UE but the UE does not acknowledge, the source base station does not forward the data packet to the target base station. The source base station sends fresh data packet to the target base station. The source base station sends fresh data by sending PDCP SDU without PDCP SN to the target base station.

[0246] In one example, in step S903, the source base station receives the information in step S902. Based on the information, the source base station forwards the data packet without PDCP SN to the target base station. For the data packet that has been assigned PDCP SN, the source base station also does not contain PDCP SN in the forwarded data packet.

[0247] In one example, if the source base station supports the architecture of separation of source base station central unit user plane and source base station central unit control plane, the source base station central unit control plane entity can inform the source base station central unit user plane entity that it is not necessary to forward the PDCP SDU containing PDCP SN to the target base station through explicit indication or implicit indication. The source base station central unit control plane entity informs the source base station central unit user plane entity that it is not necessary to forward the PDCP SDU containing PDCP SN to the target base station or does not contain PDCP SN in the forwarded data packet, which can be PDCP SDU.

[0248] In the explicit indication, the source base station central unit control plane entity sends indication information to the source base station central unit user plane entity.

[0249] The source base station central unit user plane entity determines, according to the indication information, not to forward PDCP SDUs containing PDCP SNs to the target base station, but to forward fresh data to the target base station. The fresh data is PDCP SDUs not containing PDCP SNs. The source base station central unit user plane entity forwards, according to the indication information, PDCP SDUs not containing PDCP SNs to the target base station. For data packets that have been assigned PDCP SNs, the source base station also does not contain PDCP SNs in the forwarded data packets.

[0250] In one example, the indication information can indicate at least one of the following: whether full configuration or differential configuration; whether PDCP SN status is preserved; whether only new data is sent; whether PDCP SDUs containing PDCP SNs are sent; whether PDCP data packets sent to a user equipment (UE) that have not been acknowledged by the UE are sent; whether PDCP SNs are contained in the forwarded data packets; and whether only PDCP SDUs not containing PDCP SNs are sent.

[0251] In the implicit indication manner, the source base station central unit control plane entity sends tunnel information for data forwarding without requesting PDCP SN status information, to indicate the above information, or to indicate that the source base station central unit control plane entity does not send PDCP SN status information to the target base station.

[0252] By not requesting PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status information is not preserved or other above information or the source base station central unit control plane entity does not send PDCP SN status information to the target base station, so that the source base station central unit user plane entity does not forward PDCP SDUs containing PDCP SNs to the target base station, but forwards fresh data to the target base station. The fresh data is sent by PDCP SDUs not containing PDCP SNs. Or the source base station central unit user plane entity forwards data packets not containing PDCP SNs to the target base station. For data packets that have been assigned PDCP SNs, the source base station also does not contain PDCP SNs in the forwarded data packets.

[0253] For a DRB that the source base station central unit control plane entity requests to modify or establish, if the source base station central unit control plane entity does not request PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status of the DRB is not preserved, so that the source base station central unit user plane entity only forwards fresh data to the target base station, but does not forward PDCP SDUs containing PDCP SNs to the target base station. The fresh data is sent by PDCP SDUs not containing PDCP SNs.

[0254] For a DRB requested to be modified or established by the source base station central unit control plane entity, if the source base station central unit control plane entity does not request PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status of the DRB is not reserved, and thus forwards the PDCP SDU without PDCP SN to the target base station. For the data packets that have been allocated PDCP SN, the source base station central unit user plane entity also does not include PDCP SN in the forwarded data packets.

[0255] According to the embodiment of the present application, the source base station, in particular the source base station central unit control plane entity, can know whether the PDCP SN status is maintained, and thus sends the appropriate data forwarding information to the source base station central unit user plane entity. In addition, the source base station central unit user plane entity only forwards the required data packets to the target base station, avoiding unnecessary data transmission and resource waste, improving the efficiency of data forwarding, and reducing data loss.

[0256] Figure 10 FIG. 1 is a schematic flow chart illustrating an example of a method 1000 for supporting handover according to an embodiment of the present application. The method 1000 can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0257] At step S1001, the target base station or the target base station central unit control plane entity receives a handover request message. The handover request message is received from the source base station or the source base station central unit control plane entity or from the core network. The handover request message received from the source base station or the source base station central unit control plane entity is an Xn application protocol (AP) message or other inter-base station message. The handover request message received from the core network is an NGAP message or other message between the base station and the core network.

[0258] For the handover request message received from the core network, the handover request message includes a handover type.

[0259] The target base station or the target base station central unit control plane entity decides whether to use full configuration or differential configuration. The target base station or the target base station central unit control plane entity decides whether to use full configuration or differential configuration for each established DRB.

[0260] Step S1002, the target base station or target base station central unit control plane entity sends information of full configuration or delta configuration to the source base station or source base station central unit control plane entity. The target base station or target base station central unit control plane entity can send the information to the source base station or source base station central unit control plane entity through interface messages between the target base station and the source base station. The target base station or target base station central unit control plane entity can also send the information to the source base station or source base station central unit control plane entity through the core network, such as sending the information of full configuration or delta configuration to the source base station or source base station central unit control plane entity through a target-to-source transparent transmitter. The full configuration or delta configuration can be for each DRB.

[0261] For handover preparation being a handover directly performed between base stations (e.g. Xn handover), the target base station sends the information to the source base station or source base station central unit control plane entity through a request acknowledgement message.

[0262] For handover preparation being a handover performed through the core network (e.g. NG handover), the target base station sends the information through a handover request acknowledgement from the target base station to the core network and a handover command message from the core network to the source base station, where the interaction between core network entities is omitted.

[0263] Step S1003, the source base station receives the information in step S1002. The source base station does not forward data packets containing PDCP SNs to the target base station. For PDCP data packets sent by the source base station to the UE but not acknowledged by the UE, the source base station does not forward the data packets to the target base station. The source base station sends fresh data packets to the target base station. The source base station forwards fresh data to the target base station by sending PDCP SDUs that do not contain PDCP SNs.

[0264] In one example, the source base station receives the information in step S1002, and the source base station forwards data packets that do not contain PDCP SNs to the target base station. The forwarded data packets can be PDCP SDUs. For data packets that have been assigned PDCP SNs, the source base station also does not contain PDCP SNs in the forwarded data packets.

[0265] If the source base station supports a user plane and control plane separated architecture, the source base station central unit control plane entity can inform the source base station central unit user plane entity that it does not need to forward PDCP SDUs containing PDCP SNs to the target base station or forward PDCP SDUs that do not contain PDCP SNs to the target base station through several ways:

[0266] Method one: the source base station central unit control plane entity sends indication information to the source base station central unit user plane entity, and the source base station central unit user plane entity does not forward PDCP SDUs containing PDCP SN to the target base station according to the indication information, but only forwards fresh data to the target base station. The fresh data is PDCP SDU without PDCP SN. Or the source base station central unit user plane entity forwards data packets without PDCP SN to the target base station according to the indication information. The forwarded data packets can be PDCP SDUs. For data packets that have been allocated PDCP SN, the source base station also does not contain PDCP SN in the forwarded data packets. The indication information can be information of full configuration or delta configuration, or the indication information is information of whether to retain PDCP SN state, or the indication information is information of whether to only forward fresh data, or the indication information is information of whether to forward PDCP SDUs containing PDCP SN, or information of whether to forward PDCP data packets sent to the UE without confirmation of the UE, or information of not needing PDCP SN, or the indication information is information of only forwarding PDCP SDUs without PDCP SN, etc.

[0267] Method two: the source base station central unit control plane entity sends channel information for data forwarding to the source base station central unit user plane entity, and the source base station central unit control plane entity does not request PDCP SN state information. By not requesting PDCP SN state information, the source base station central unit user plane entity knows that the PDCP SN state information is not retained or other above-mentioned information or the source base station central unit control plane entity does not send SN state information to the target base station, so as to not forward PDCP SDUs containing PDCP SN to the target base station, but only forward fresh data to the target base station. The fresh data is sent by PDCP SDUs without PDCP SN. Or the source base station central unit user plane entity forwards data packets without PDCP SN to the target base station. For the DRB requested by the source base station central unit control plane entity to modify or establish, if the source base station central unit control plane entity does not request PDCP SN state information, the source base station central unit user plane entity knows that the PDCP SN state of the DRB is not retained, so as to only forward fresh data to the target base station, and not forward PDCP SDUs containing PDCP SN to the target base station. The fresh data is sent by PDCP SDUs without PDCP SN. Or the source base station central unit user plane entity forwards data packets without PDCP SN to the target base station.

[0268] The source base station central unit user plane entity does not forward PDCP SDUs containing PDCP SNs to the target base station, but only forwards fresh data to the target base station. The fresh data are PDCP SDUs not containing PDCP SNs. Alternatively, the source base station central unit user plane entity forwards data packets not containing PDCP SNs to the target base station. The data packets can be PDCP SDUs. For data packets that have been assigned PDCP SNs, the source base station also does not contain PDCP SNs in the forwarded data packets.

[0269] So far, the method 1000 for supporting handover according to the present application has been described. Through the method, the source base station, in particular the source base station central unit control plane entity, can know whether the PDCP SN state is maintained, so as to send appropriate data forwarding information to the source base station central unit user plane entity, which only forwards the required data packets to the target base station, thereby avoiding unnecessary data transmission and resource waste, improving the efficiency of data forwarding, and reducing data loss.

[0270] Figure 11 FIG. 11 is a flowchart illustrating an example of a method 1100 for supporting handover according to an embodiment of the present application. The method 1100 can be used for intra-system handover or inter-system handover, and can be performed at the source base station central unit control plane entity side.

[0271] As shown in FIG. 11, in the method 1100, at step S1101, a handover-related message is received. Figure 11

[0272] At step S1102, information for data forwarding is indicated to a source base station central unit user plane entity, wherein the source base station central unit user plane entity sends PDCP service data units (SDUs) not containing PDCP SNs to a target base station based on the information for data forwarding.

[0273] Alternatively, at step S1102, information for data forwarding is indicated to a source base station central unit user plane entity, wherein the source base station central unit user plane entity forwards PDCP SDUs not containing PDCP SNs to a target base station based on the information for data forwarding.

[0274] ​In one example, the handover related message is one of a handover request acknowledge message and a handover command message, and the handover related message indicates whether full configuration or differential configuration or indicates whether packet data convergence protocol (PDCP) sequence number (SN) status is retained. For example, at step S1101, the source base station central unit control plane entity can receive the handover command message or the handover request acknowledge message. The handover request acknowledge message can be received from the target base station or the target base station central unit control plane entity. The handover command message is received from the core network.

[0275] The handover request acknowledge message or the handover command message contains information of whether full configuration or differential configuration or information of whether PDCP SN status is retained.

[0276] In one example, at step S1102, the source base station central unit control plane entity can indicate information for data forwarding to the source base station central unit user plane entity by an explicit indication method or an implicit indication method.

[0277] In the explicit indication method, the information for data forwarding can include indication information sent by a bearer context modification request message, and the indication information can indicate at least one of the following: information of whether PDCP SN status is retained; whether only new data is sent; whether PDCP SDU containing PDCP SN is sent; whether PDCP data packet sent to a user equipment (UE) without acknowledgement by the UE is sent; whether PDCP SN is contained in forwarded data packet; and whether only PDCP SDU not containing PDCP SN is sent.

[0278] In one example, the source base station central unit user plane entity knows to forward only fresh data to the target base station and not to forward PDCP SDU containing PDCP SN to the target base station when at least one of the following is determined according to the indication information: PDCP SN status is not retained; only new data is sent; PDCP SDU containing PDCP SN is not sent; PDCP data packet sent to a user equipment (UE) without acknowledgement by the UE is not sent; and only PDCP SDU not containing PDCP SN is sent.

[0279] In one example, the source base station central unit user plane entity knows to forward PDCP SDU not containing PDCP SN to the target base station when at least one of the following is determined according to the indication information: PDCP SN status is not retained; only new data is sent; PDCP SDU containing PDCP SN is not sent; PDCP data packet sent to a user equipment (UE) without acknowledgement by the UE is not forwarded; and only PDCP SDU not containing PDCP SN is sent.

[0280] In the implicit indication method, the source gNB-CU-CP entity can send the tunnel information for data forwarding without requesting the PDCP SN status information to indicate that the PDCP SN status is not preserved or the source gNB-CU-CP entity does not send the PDCP SN status information to the target gNB. By not requesting the PDCP SN status information, the source gNB-CU-UP entity knows that the PDCP SN status is not preserved or the source gNB-CU-CP entity does not send the SN status information to the target gNB, and thus does not forward the PDCP SDUs containing PDCP SN to the target gNB, but only forwards fresh data to the target gNB. The fresh data is sent by PDCP SDUs not containing PDCP SN. Or the source gNB-CU-UP entity forwards data packets not containing PDCP SN to the target gNB.

[0281] For a DRB requested to be modified or established by the source gNB-CU-CP entity, if the source gNB-CU-CP entity does not request the PDCP SN status information, the source gNB-CU-UP entity knows that the PDCP SN status of the DRB is not preserved, and thus only forwards fresh data to the target gNB, but does not forward PDCP SDUs containing PDCP SN to the target gNB. The fresh data is sent by PDCP SDUs not containing PDCP SN.

[0282] For a DRB requested to be modified or established by the source gNB-CU-CP entity, if the source gNB-CU-CP entity does not request the PDCP SN status information, the source gNB-CU-UP entity knows that the PDCP SN status of the DRB is not preserved, and thus only forwards fresh data to the target gNB, but does not forward PDCP SDUs containing PDCP SN to the target gNB. The fresh data is sent by PDCP SDUs not containing PDCP SN.

[0283] In addition, the source gNB-CU-UP entity can not forward data packets sent to the UE but not acknowledged by the UE.

[0284] The source base station central unit user plane entity knows the information of data forwarding through the explicit indication method or the implicit indication method in step S1102. Corresponding to the implicit indication method, the source base station central unit user plane entity knows the information of PDCP SN status reservationless according to that the source base station central unit control plane entity does not request PDCP SN status information, or the source base station central unit control plane entity does not send PDCP SN status information to the target base station, so as not to forward the PDCP SDU containing PDCP SN to the target base station, but only to forward fresh data to the target base station. The fresh data is sent through the PDCP SDU not containing PDCP SN. Or the source base station central unit user plane entity forwards the data packet not containing PDCP SN to the target base station. For the data packet that has been allocated PDCP SN, the source base station central unit user plane entity also does not contain PDCP SN in the forwarded data packet.

[0285] According to the embodiment of the present application, the source base station central unit control plane entity can send the appropriate data forwarding information to the source base station central unit user plane entity, and the source base station central unit user plane entity only forwards the required data packet to the target base station, which avoids unnecessary data transmission and resource waste, improves the efficiency of data forwarding, and reduces data loss.

[0286] Figure 12 FIG. 12 is a flowchart illustrating an example of a method 1200 for supporting handover according to an embodiment of the present application. The method can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0287] In step S1201, the source base station central unit control plane entity receives a handover command message or a handover request acknowledgement message. The handover request acknowledgement message is received from the target base station or the target base station central unit control plane entity. The handover command message is received from the core network.

[0288] The handover request acknowledgement message or the handover command message contains information of whether it is a full configuration or a delta configuration, or information of whether PDCP SN status is reserved.

[0289] In step S1202, the source base station central unit control plane entity explicitly or implicitly informs the source base station central unit user plane entity of the data forwarding information. The data forwarding information is whether to retain the PDCP SN status information, or whether to only forward fresh data information, or whether to forward PDCP SDUs containing PDCP SN information, or whether to forward PDCP data packets sent to the UE without being confirmed by the UE information, or PDCP SN information is not required, or only forward PDCP SDUs not containing PDCP SN information, and the like. The explicit manner is to indicate the data forwarding information by including an information element. The information element can be included in the bearer context modification request message.

[0290] The implicit manner is that the source base station central unit control plane entity does not send the request PDCP SN status information to the source base station central unit user plane entity. The source base station central unit control plane entity sends the channel information for data forwarding to the source base station central unit user plane entity. By not requesting the PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status information is not retained or other above-mentioned information or the source base station central unit control plane entity does not send the SN status information to the target base station, so as to not forward the PDCP SDUs containing PDCP SN to the target base station, and only forward fresh data to the target base station. The fresh data is sent by PDCP SDUs not containing PDCP SN. Or the source base station central unit user plane entity forwards the data packets not containing PDCP SN to the target base station. For the data packets that have been allocated PDCP SN, the source base station central unit user plane entity also does not contain PDCP SN in the forwarded data packets. For the DRB requested by the source base station central unit control plane entity to modify or establish, if the source base station central unit control plane entity does not request the PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status of the DRB is not retained, so as to only forward fresh data to the target base station, and not forward PDCP SDUs containing PDCP SN to the target base station. The fresh data is sent by PDCP SDUs not containing PDCP SN. Or the source base station central unit user plane entity forwards the data packets not containing PDCP SN to the target base station. For the data packets that have been allocated PDCP SN, the source base station central unit user plane entity also does not contain PDCP SN in the forwarded data packets.

[0291] In step S1203, the source base station central unit user plane entity forwards PDCP SDUs without PDCP SN to the target base station, and does not forward PDCP SDUs with PDCP SN to the target base station. Only fresh data is forwarded to the target base station. The fresh data is sent through PDCP SDUs without PDCP SN. The source base station central unit user plane entity does not forward data packets for which the UE has not acknowledged. The source base station central unit user plane entity knows the data forwarding information through the explicit or implicit manner described in step S1202. For the implicit manner, the source base station central unit user plane entity knows that the PDCP SN status information is not reserved according to the fact that the source base station central unit control plane entity has not requested the PDCP SN status information, or the source base station central unit control plane entity has not sent the SN status information to the target base station, so that the source base station central unit user plane entity does not forward PDCP SDUs with PDCP SN to the target base station, and only forwards fresh data to the target base station. The fresh data is sent through PDCP SDUs without PDCP SN.

[0292] Alternatively, in step S1203, the source base station central unit user plane entity forwards data packets without PDCP SN to the target base station. For data packets for which PDCP SN has been allocated, the source base station central unit user plane entity also does not include PDCP SN in the forwarded data packets.

[0293] So far, the method 1200 for supporting handover according to the present application has been described. Through the method, the source base station central unit control plane entity sends appropriate data forwarding information to the source base station central unit user plane entity, the source base station central unit user plane entity only forwards necessary data packets to the target base station, unnecessary data transmission and resource waste are avoided, the data forwarding efficiency is improved, and data loss is reduced.

[0294] Figure 13 FIG. 13 is a flowchart illustrating an example of a method 1300 for supporting handover according to an embodiment of the present application. The method 1300 can be used for intra-system handover or inter-system handover, and can be performed at the source base station central unit user plane entity side.

[0295] As shown in FIG. 13, in the method 1300, in step S1301, information indicating data forwarding is received. Figure 13

[0296] In step S1302, based on the information indicating data forwarding, PDCP service data unit (SDU) without PDCP SN is sent to the target base station.

[0297] ​At step S1302, based on the information for data forwarding, the source base station does not send PDCP service data unit (SDU) containing PDCP SN to the destination base station. For the data packets that have been assigned PDCP SN, the source base station also does not include PDCP SN in the forwarded data packets.

[0298] In one example, at step S1301, the information for data forwarding can be received by an explicit indication method or an implicit indication method.

[0299] In the explicit indication method, the source base station central unit user plane entity can receive the information for data forwarding sent by the source base station central unit control plane entity. The information for data forwarding includes indication information received by the bearer context modification request message, and the indication information can indicate at least one of the following: whether PDCP SN status is preserved; whether only new data is sent; whether PDCP SDU containing PDCP SN is sent; whether PDCP data packets sent to user equipment (UE) without acknowledgement by the UE are sent; whether PDCP SN is sent; and whether only PDCP SDU not containing PDCP SN is sent.

[0300] In one example, when at least one of the following is determined according to the indication information, the source base station central unit user plane entity knows that only fresh data is forwarded to the destination base station, and PDCP SDU containing PDCP SN is not forwarded to the destination base station: PDCP SN status is not preserved; only new data is sent; PDCP SDU containing PDCP SN is not sent; PDCP data packets sent to user equipment (UE) without acknowledgement by the UE are not sent; PDCP SN is not sent; and only PDCP SDU not containing PDCP SN is sent.

[0301] In one example, when at least one of the following is determined according to the indication information, the source base station central unit user plane entity knows that PDCP SDU not containing PDCP SN is forwarded to the destination base station: PDCP SN status is not preserved; only new data is sent; PDCP SDU containing PDCP SN is not sent; PDCP data packets sent to user equipment (UE) without acknowledgement by the UE are not sent; PDCP SN is not sent; and only PDCP SDU not containing PDCP SN is sent.

[0302] In the implicit indication method, the source base station central unit control plane entity receives the channel information for data forwarding without requesting PDCP SN status information, to indicate that PDCP SN is not preserved or the source base station central unit control plane entity does not send PDCP SN status information to the destination base station.

[0303] The source base station central unit control plane entity sends the tunnel information for data forwarding to the source base station central unit user plane entity. By not requesting the PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN is not reserved or the source base station central unit control plane entity does not send the PDCP SN status information to the target base station, so that it does not forward the PDCP SDUs containing the PDCP SN to the target base station, but only forwards the fresh data to the target base station. The fresh data is sent by PDCP SDUs not containing the PDCP SN.

[0304] The source base station central unit control plane entity sends the tunnel information for data forwarding to the source base station central unit user plane entity. By not requesting the PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN is not reserved or the source base station central unit control plane entity does not send the PDCP SN status information to the target base station, so that it forwards the PDCP SDUs not containing the PDCP SN to the target base station.

[0305] For a DRB requested to be modified or established by the source base station central unit control plane entity, if the source base station central unit control plane entity does not request the PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status of the DRB is not reserved, so that it only forwards the fresh data to the target base station, but does not forward the PDCP SDUs containing the PDCP SN to the target base station. The fresh data is sent by PDCP SDUs not containing the PDCP SN.

[0306] For a DRB requested to be modified or established by the source base station central unit control plane entity, if the source base station central unit control plane entity does not request the PDCP SN status information, the source base station central unit user plane entity knows that the PDCP SN status of the DRB is not reserved, so that it forwards the PDCP SDUs not containing the PDCP SN to the target base station. For data packets that have been allocated the PDCP SN, the source base station central unit user plane entity also does not contain the PDCP SN in the forwarded data packets.

[0307] The source base station central unit user plane entity forwards PDCP SDUs without PDCP SN to the target base station, and does not forward PDCP SDUs with PDCP SN to the target base station. The PDCP SDUs without PDCP SN can be fresh data. The source base station central unit user plane entity does not forward data packets sent to the UE but not acknowledged by the UE. The source base station central unit user plane entity knows the information of data forwarding through the explicit indication method or the implicit indication method in step S1301. Corresponding to the implicit indication method, the source base station central unit user plane entity knows that the PDCP SN status is not reserved according to the fact that the source base station central unit control plane entity does not request PDCP SN status information, or the source base station central unit control plane entity does not send PDCP SN status information to the target base station, so that the source base station central unit user plane entity does not forward PDCP SDUs with PDCP SN to the target base station, but only forwards fresh data to the target base station. The fresh data is sent through PDCP SDUs without PDCP SN. The source base station central unit user plane entity does not forward data packets sent to the UE but not acknowledged by the UE. Or the source base station central unit user plane entity forwards data packets without PDCP SN to the target base station.

[0308] According to the embodiment of the present application, the source base station central unit user plane entity can only forward the required data packets to the target base station, avoiding unnecessary data transmission and resource waste, improving the efficiency of data forwarding, and reducing data loss.

[0309] Figure 14 FIG. 14 is a flowchart illustrating an example of a method 1400 for supporting handover according to an embodiment of the present application. The method 1400 can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0310] In step S1401, the source base station central unit user plane entity receives the information of data forwarding and the channel information for data forwarding sent by the source base station central unit control plane entity. The information of data forwarding includes information of whether to forward PDCP SDUs with PDCP SN, or information of whether the PDCP SN status is reserved, or information of whether to only forward fresh data, or information of whether to forward PDCP data packets sent to the UE but not acknowledged by the UE, or information of whether to include PDCP SN in the forwarded data packets, or information of whether to only forward PDCP SDUs without PDCP SN, etc. The information of data forwarding can be in an explicit manner or an implicit manner. The explicit manner is to directly include an information element to indicate the above-mentioned information of data forwarding. The information element can be included in the bearer context modification request message.

[0311] The implicit way is that the source gNB-CU-CP entity does not send a request for PDCP SN status information to the source gNB-CU-UP entity. The source gNB-CU-CP entity sends tunnel information for data forwarding to the source gNB-CU-UP entity. By not requesting PDCP SN status information, the source gNB-CU-UP entity knows that the PDCP SN status information is not reserved or the source gNB-CU-CP entity does not send the SN status information to the target gNB, so that it forwards no PDCP PDU containing PDCP SN to the target gNB, or no PDCP SDU containing PDCP SN to the target gNB, or only fresh data to the target gNB, which is sent by PDCP SDUs not containing PDCP SN. For a DRB that the source gNB-CU-CP entity requests modification or establishment, if the source gNB-CU-CP entity does not request PDCP SN status information, the source gNB-CU-UP entity knows that the PDCP SN status information of the DRB is not reserved, so that it only forwards fresh data to the target gNB, and does not forward PDCP SDUs containing PDCP SN to the target gNB. The fresh data is sent by PDCP SDUs not containing PDCP SN. Or the source gNB-CU-UP entity forwards no PDCP PDU containing PDCP SN to the target gNB.

[0312] In step S1402, the source gNB-CU-UP entity forwards no PDCP PDU containing PDCP SN to the target gNB, and forwards PDCP SDUs not containing PDCP SN to the target gNB. The PDCP SDUs not containing PDCP SN can be fresh data. The source gNB-CU-UP entity does not forward data packets sent to the UE without acknowledgement. The source gNB-CU-UP entity knows the data forwarding information by the explicit way or the implicit way described in step S1401. Corresponding to the implicit way, the source gNB-CU-UP entity knows that the PDCP SN status information is not reserved or the source gNB-CU-CP entity does not send the SN status information to the target gNB according to the source gNB-CU-CP entity not requesting PDCP SN status information, so that it forwards no PDCP PDU containing PDCP SN to the target gNB, or no PDCP SDU containing PDCP SN to the target gNB. Or only fresh data to the target gNB, which is sent by PDCP SDUs not containing PDCP SN. The source gNB-CU-UP entity does not forward data packets sent to the UE without acknowledgement.

[0313] So far, the description of the method 1400 for supporting handover according to the present application is completed. Through the method, the source base station central unit user plane entity only forwards the required data packets to the target base station, avoiding unnecessary data transmission and resource waste, improving the efficiency of data forwarding, and reducing data loss.

[0314] Figure 15 An exemplary flowchart of a method 1500 for supporting handover according to an embodiment of the present application is shown. The method 1500 can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0315] In step S1501, the target base station central unit control plane entity receives a handover request message from the source base station or from the core network. The handover request message received from the source base station is an inter-base station interface application layer message, such as an XnAP message. The handover request message received from the core network is an application layer message of the base station and core network interface, such as an NGAP message. The handover request message contains the configuration information of the UE at the source base station end, which includes DRB configuration information and / or Qos flow to DRB mapping. The message contains the E-RAB identifier of the Qos flow mapping.

[0316] The target base station central unit control plane entity decides the target end DRB configuration information and / or Qos Flow to DRB mapping. The target base station includes the target end DRB configuration information and / or Qos Flow to DRB mapping in the handover command message, which is sent to the UE through the source base station.

[0317] In step S1502, the target base station central unit control plane entity sends the configuration information of the source end DRB and the configuration information of the target end DRB to the target base station central unit user plane entity. And / or, the target base station central unit control plane entity sends the source end Qos Flow to DRB mapping and the target end Qos flow to DRB mapping to the target base station central unit user plane entity. For inter-system handover from a 4G system to a 5G system, the configuration information of the source DRB can also be referred to as the configuration information of the source E-RAB, and the source end Qos Flow to DRB mapping is also the Qos flow to E-RAB mapping.

[0318] The target base station central unit control plane entity can decide to use the same DRB configuration as the source end or a different DRB configuration.

[0319] If the destination base station central unit control plane entity decides to use the same DRB configuration and the same Qos flow to DRB mapping as the source base station, it sends the information, i.e. the DRB configuration, to the destination base station central unit user plane entity through the DRB to be established and the Qos flow information to be established on the DRB. The destination base station central unit control plane entity sends the information to the destination base station central unit user plane entity through the bearer context setup request message or the bearer context modification request message. The destination base station central unit control plane entity sends the mapping relationship to the destination base station central unit user plane entity through the Qos flow(s) information to be established contained in the DRB to be established in the bearer context setup request message or the bearer context modification request message. The DRB to be established is the DRB to be established contained in the PDU session resource setup list in the bearer context setup request message or the DRB to be established contained in the PDU session resource setup list (also called PDU session resource setup modification list) in the bearer context modification request message. For the EN-DC to SA handover and the source secondary base station and the destination base station are shared, the destination base station central unit control plane entity can send the mapping relationship to the destination base station central unit user plane entity through the Qos flow(s) information to be established contained in the DRB to be established in the bearer context modification request message.

[0320] If the destination base station central unit control plane entity decides to use the same Qos flow to DRB mapping as the source base station, it sends the mapping relationship to the destination base station central unit user plane entity. The destination base station central unit control plane entity sends the mapping relationship to the destination base station central unit user plane entity through the bearer context setup request message or the bearer context modification request message. The destination base station central unit control plane entity sends the mapping relationship to the destination base station central unit user plane entity through the Qos flow(s) information to be established contained in the DRB to be established in the bearer context setup request message or the bearer context modification request message. The DRB to be established is the DRB to be established contained in the PDU session resource setup list in the bearer context setup request message or the DRB to be established contained in the PDU session resource setup list (also called PDU session resource setup modification list) in the bearer context modification request message. For the EN-DC to SA handover and the source secondary base station and the destination base station are shared, the destination base station central unit control plane entity can send the mapping relationship to the destination base station central unit user plane entity through the Qos flow(s) information to be established contained in the DRB to be established in the bearer context modification request message.

[0321] If the destination base station central unit control plane entity decides to use different DRB configuration and / or different Qos flow to DRB mapping than the source base station, in order to ensure lossless during handover, the destination base station central unit control plane entity can decide to temporarily configure the same DRB and / or the same Qos flow to DRB mapping as the source base station for handling the data forwarded by the source base station. The destination DRB configuration and Qos flow to DRB mapping decided by the destination base station central unit control plane entity is used by the destination base station central unit user plane entity for handling the new data received from the core network. For inter-system handover from 4G system to 5G system, the destination base station central unit control plane entity can decide to temporarily configure the same DRB (or E-RAB) and / or the same Qos flow to DRB (or E-RAB) mapping as the source base station for handling the data forwarded by the source base station. The destination DRB configuration and Qos flow to DRB mapping decided by the destination base station central unit control plane entity is used by the destination base station central unit user plane entity for handling the new data received from the core network.

[0322] When the destination base station central unit control plane entity decides the DRB configuration of the destination end and the DRB configuration of the source end are different, the destination base station central unit control plane entity sends the configuration information of the source end DRB to the destination base station central unit user plane entity. The destination base station central unit control plane entity can send the configuration information of the source end DRB and the configuration information of the destination end DRB directly to the destination base station central unit user plane entity, or send the configuration information of the destination end DRB and the delta configuration of the source end and the destination end to the destination base station central unit user plane entity, or send the configuration information of the source end DRB and the delta configuration of the source end and the destination end to the destination base station central unit user plane entity. Through the configuration information of the destination end DRB and the delta configuration information of the source end and the destination end, the destination base station central unit user plane entity knows the configuration information of the source end DRB, or through the configuration information of the source end DRB and the delta configuration information of the source end and the destination end, the destination base station central unit user plane entity knows the configuration information of the destination end DRB. If the destination base station central unit control plane entity sends the configuration information of the source end DRB and the configuration information of the destination end DRB directly to the destination base station central unit user plane entity, the Qos flow information to be established contained in the corresponding source end DRB configuration information is the Qos flow(s) mapped by the source end to the DRB. The Qos flow information to be established contained in the destination end DRB configuration information is the Qos flow(s) mapped by the destination end to the DRB. The configuration information of the DRB is contained in the DRB information to be established or the DRB information to be modified. The destination end DRB configuration information can be represented by the DRB to be established or the DRB to be modified in the existing message, and a new information element, for example, the source end DRB configuration information, is defined to represent the source end DRB configuration information. The source end DRB configuration information can be represented by the DRB to be established or the DRB to be modified in the existing message, and a new information element, for example, the destination end DRB configuration information or the updated DRB configuration information, is defined to represent the destination end DRB configuration information. If the destination base station central unit control plane entity sends the configuration information of the destination end DRB and the delta configuration of the source end and the destination end to the destination base station central unit user plane entity, the configuration information of the destination end DRB and the Qos flow(s) mapped by the destination end to the DRB are contained in the DRB information to be established or the DRB information to be modified, and the delta configuration and / or the Qos flow(s) mapped by the source end to the DRB are also contained in the DRB information to be established or the DRB information to be modified. If a certain DRB is only the configuration of the source end, and the corresponding DRB is not used by the destination end, the source end DRB indication information is contained in the DRB to be established or the DRB to be modified.If the source DRB configuration information and the delta configuration from source to destination are sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity, the DRB to be established or the DRB to be modified information contains the source DRB configuration information and the Qos flow(s) mapped to the DRB at the source, and the DRB to be established or the DRB to be modified information also contains the delta configuration and / or the Qos flow(s) mapped to the DRB at the destination. If a DRB is only configured at the source, the destination does not use the corresponding DRB, and the DRB to be established or the DRB to be modified contains the destination DRB indication information.

[0323] If the destination base station central unit control plane entity decides to use different Qos flow to DRB mapping from the source base station, in order to ensure lossless during the handover process, the destination base station central unit control plane entity can decide to temporarily configure the same Qos flow to DRB mapping as the source base station for processing the data forwarded by the source base station. The destination base station central unit control plane entity decides the destination Qos flow to DRB mapping for the destination base station central unit user plane entity to process the new data received from the core network. For inter-system handover from 4G system to 5G system, the destination base station central unit control plane entity can decide to temporarily configure the same Qos flow to DRB (or E-RAB) mapping as the source base station for processing the data forwarded by the source base station. The destination base station central unit control plane entity decides the destination DRB configuration and Qos flow to DRB mapping for the destination base station central unit user plane entity to process the new data received from the core network.

[0324] The destination base station central unit control plane entity sends the mapping of source Qos Flows to DRBs and / or the mapping of destination Qos Flows to DRBs to the destination base station central unit user plane entity. The destination Qos Flow information to be established and / or the source Qos Flow information to be established is included in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity. The destination Qos Flow information to be established includes one or more Qos Flows mapped to the DRB at the destination. The source Qos Flow information to be established includes one or more Qos Flows mapped to the DRB at the source. If the DRB information to be established only includes the destination Qos Flow information to be established, it means that the DRB is only used to process new data from the core network, and the corresponding DRB is not used at the source. If the DRB information to be established only includes the source Qos Flow information to be established, it means that the DRB is only used to process data forwarded from the source base station, and the corresponding DRB is not used at the destination. It means that the DRB is the old DRB configuration at the source, and the destination base station central unit user plane entity can release the DRB after receiving the end marker packet.

[0325] The destination Qos Flow information to be established can be indicated by the existing Qos Flow information to be established in the DRB information to be established in the interface message between the base station central unit control plane entity and the base station central unit user plane entity. In this case, a new information element (IE) is needed to indicate the mapping information at the source or the source Qos Flow information to be established, such as the source Qos Flow information to be established or the old Qos Flow information to be established. The existing Qos Flow information to be established in the DRB information to be established is a mandatory field. In order to indicate that the DRB is the old DRB at the source and is not used at the destination, the source Qos Flow information to be established or the old Qos Flow information to be established (i.e., the information of the Qos Flows mapped to the DRB at the source) is needed in the DRB information to be established. In order to handle this case, a source DRB configuration indication or an old DRB configuration indication can be included in the DRB information to be established in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, so that the base station central unit user plane entity can ignore the existing Qos Flow information to be established. This method can also be used for the bearer context modification message.

[0326] The source end to be established Qos flow information can be represented by the existing to be established Qos Flow information in the to be established DRB information in the base station central unit control plane entity and base station central unit user plane entity interface message, a new information element (IE) is needed to be defined, for example, the destination to be established Qos flow information or the new to be established Qos flow information to represent the mapping information of the destination or the destination to be established Qos flow information. The existing to be established Qos Flow information in the to be established DRB information is a mandatory field, in order to represent that the DRB is the destination end DRB, the to be established DRB information only needs to contain the destination to be established Qos flow information or the new to be established Qos flow information (i.e. the information of the Qos flow of the destination mapped to the DRB), in order to handle this case, the destination DRB configuration indication or the new DRB configuration indication can be contained in the to be established DRB information in the base station central unit control plane entity and base station central unit user plane entity interface message, so that the base station central unit user plane entity can ignore the existing to be established Qos Flow information. This method can also be used in the bearer context modification message.

[0327] The destination flow mapping information and / or the source flow mapping information is contained in the to be modified DRB information sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity. The destination flow mapping information contains one or more Qos flows mapped to the DRB at the destination. The source flow mapping information contains one or more Qos flows mapped to the DRB at the source. If only the destination flow mapping information is contained in the to be modified DRB information, it means that the DRB is only used to process new data from the core network, the corresponding DRB is not used at the source end. If only the source flow mapping information is contained in the to be modified DRB information, it means that the DRB is only used to process data forwarded from the source base station, the corresponding DRB is not used at the destination, it means that the DRB is the old DRB configuration at the source end, the destination base station central unit user plane entity can release the DRB after receiving the end marker packet.

[0328] The Qos flow(s) mapped to the DRB at the destination can be represented by the existing flow mapping information in the to be modified DRB information in the base station central unit control plane entity and base station central unit user plane entity interface message, a new information element (IE) is needed to be defined, for example, the source flow mapping information or the old flow mapping information to represent the Qos flow(s) mapped to the DRB at the source.

[0329] The source end mapping to the Qos flow(s) of the DRB can be expressed by the existing flow mapping information in the DRB information to be modified in the base station central unit control plane entity and base station central unit user plane entity interface message, so a new information element (IE) such as destination flow mapping information or new flow mapping information needs to be defined to express the destination end mapping to the Qos flow(s) of the DRB.

[0330] The destination base station central unit control plane entity can send the above information to the destination base station central unit user plane entity in the bearer context setup request or bearer context modification request message or other messages. The DRB to be established is the DRB to be established contained in the PDU session resource setup list in the bearer context setup request message or the DRB to be established contained in the PDU session resource setup list (also called PDU session resource setup modification list) in the bearer context modification request message. For EN-DC to SA handover and shared source secondary base station and destination base station, the destination base station central unit control plane entity can send the above information to the destination base station central unit user plane entity in the DRB to be established in the bearer context modification request message.

[0331] In step S1503, the destination base station central unit user plane entity receives the above information from the destination base station central unit control plane entity, and the destination base station central unit user plane entity saves the received information. The destination base station central unit user plane entity allocates channel information for the DRB requesting data forwarding and sends it to the destination base station central unit control plane entity.

[0332] The destination gNB-CU-CP entity sends a UE context setup request message to the destination gNB-DU. The message contains the configuration of the source DRBs and the decided DRB configuration at the destination. Corresponding to the source DRBs, the DRBs to be setup contain the QoS flow(s) mapped on the DRB at the source. Corresponding to the decided new DRBs at the destination, the DRBs to be setup contain the QoS flow(s) decided by the destination gNB-CU-CP entity to be mapped on the DRB. If the same DRB configuration and the same QoS flow to DRB mapping as the source is used at the destination, the DRBs to be setup contain the QoS flow(s) mapped on the DRB at the source. If the same DRB configuration as the source is used at the destination but different QoS flow to DRB mapping, the DRBs to be setup can contain the QoS flow(s) mapped on the DRB at the source and / or the QoS flow(s) mapped on the DRB at the destination. The gNB-DU allocates a downlink transport layer address and a tunnel identifier for each DRB to be setup. The gNB-DU sends a UE context setup response message to the destination gNB-CU-CP entity, which contains the downlink transport layer address and the tunnel identifier allocated by the gNB-DU for each DRB. The gNB-CU-CP entity sends the downlink transport layer address and the tunnel identifier allocated by the gNB-DU for each DRB to the destination gNB-CU-UP entity. The destination gNB-CU-UP entity receives the data forwarded from the source gNB.

[0333] The destination gNB-CU-UP entity processes the data received from the source gNB using the source DRB configuration and / or the source QoS flow to DRB mapping and processes the new data received from the core network using the destination DRB configuration and / or the destination QoS flow to DRB mapping. Corresponding to the DRBs to be setup or to be modified, which do not contain the destination QoS flow information, the destination gNB-CU-UP entity can release the DRB after receiving the end marker. The destination gNB-CU-UP entity first sends the data received from the source gNB through the gNB-DU to the UE. After receiving the end marker, it starts sending the data received from the core network.

[0334] The release procedure of the old DRBs at the gNB-DU is as described in the method of Figure 25 or as follows. The old DRBs are the DRBs at the source and the destination configuration is for processing the forwarded data.

[0335] When no new data is received on a DRB within a certain time, the gNB-DU sends a UE context modification required message to the destination base station central unit control plane entity. The message contains the identity of the DRB that needs to be released. The destination base station central unit control plane entity can release the old DRB after receiving the message.

[0336] So far, the description of the method 1500 for supporting handover according to the present application is completed. Through the method, in the case that the destination base station adopts different Qos flow to DRB mapping from the source base station, the destination base station central unit control plane and the destination base station central unit user plane can be ensured to have correct processing, data loss can be avoided, the efficiency of data transmission can be improved, and the reliability of data forwarding in handover can be improved.

[0337] Figure 16 FIG. 16 is a flowchart illustrating an example of a method 1600 for supporting handover according to an embodiment of the present application. The method 1600 can be used for intra-system handover or inter-system handover, and can be performed at the destination base station central unit control plane entity side. The method includes the following steps.

[0338] As shown in FIG. 16, in the method 1600, at step S1601, a handover request message is received. Figure 16

[0339] The destination base station central unit control plane entity receives a handover request message from the source base station or from the core network. The handover request message received from the source base station is an inter-base station interface application layer message, such as an XnAP message. The handover request message received from the core network is an application layer message of the interface between the base station and the core network, such as an NGAP message. The handover request message contains the configuration information of the UE at the source base station end, and the configuration information contains the mapping of service Qos flow to DRB. The message contains the E-RAB identity of the Qos flow mapping.

[0340] The destination base station central unit control plane entity decides the configuration of the DRB at the destination end.

[0341] The destination base station central unit control plane entity decides the mapping of Qos Flow to DRB at the destination end. The destination base station contains the configuration of the DRB at the destination end and / or the mapping of Qos Flow to DRB in the handover command message, which is sent to the UE through the source base station.

[0342] ​In step S1602, the configuration information of the source DRB and the configuration information of the target DRB are sent to the user plane entity of the target base station central unit. And / or, the mapping of the source quality of service (QoS) flow to data radio bearer (DRB) and the mapping of the target QoS flow to DRB are sent to the user plane entity of the target base station central unit. Wherein, the configuration of the source DRB and / or the mapping of the QoS flow to DRB are used by the user plane entity of the target base station central unit to process the forwarded data received from the source base station, and the configuration of the target DRB and / or the mapping of the QoS flow to DRB are used by the user plane entity of the target base station central unit to process the new data received from the core network. For the inter-system handover from the 4G system to the 5G system, the configuration information of the source DRB can also be the configuration information of the source E-RAB, and the mapping of the source QoS flow to DRB can also be the mapping of the QoS flow to E-RAB.

[0343] The target base station central unit control plane entity can decide to use the same DRB configuration as the source or a different DRB configuration. If the target base station central unit control plane entity decides to use the same DRB configuration as the source, the DRB configuration information is sent to the user plane entity of the target base station central unit. If the target base station central unit control plane entity decides to use a different DRB configuration from the source, the source DRB configuration information needs to be sent to the user plane entity of the target base station central unit in addition to the target DRB configuration information. The target base station central unit control plane entity sends the information to the user plane entity of the target base station central unit through the bearer context setup request message or the bearer context modification request message. The specific sending method is the same as in step S1502, which will not be described here.

[0344] As mentioned before, if the destination base station central unit control plane entity decides the mapping of Qos flow to DRB is the same as the source base station, it sends the mapping relationship to the destination base station central unit user plane entity. The destination base station central unit control plane entity sends the mapping relationship to the destination base station central unit user plane entity through the bearer context setup request message or the bearer context modification request message. The destination base station central unit control plane entity sends the mapping relationship to the destination base station central unit user plane entity through the information of the Qos flow(s) to be established contained in the DRB to be established in the bearer context setup request message or the bearer context modification request message. The DRB to be established is the DRB to be established contained in the PDU session resource setup list in the bearer context setup request message or the DRB to be established contained in the PDU session resource setup list (also called PDU session resource setup modification list) in the bearer context modification request message. For EN-DC to SA handover and the source secondary base station and the destination base station are shared, the destination base station central unit control plane entity can send the mapping relationship to the destination base station central unit user plane entity through the information of the Qos flow(s) to be established contained in the DRB to be established in the bearer context modification request message.

[0345] If the destination base station central unit control plane entity decides the mapping of Qos flow to DRB is different from the source base station, in order to ensure the data lossless during the handover process, the destination base station central unit control plane entity temporarily configures the mapping of Qos flow to DRB which is the same as the source base station to process the data forwarded by the source base station. The mapping of Qos flow to DRB decided by the destination base station central unit control plane entity is used for the destination base station central unit user plane entity to process the new data received from the core network.

[0346] The destination base station central unit control plane entity sends the mapping of source Qos Flows to DRBs and the mapping of destination Qos Flows to DRBs to the destination base station central unit user plane entity. The destination Qos Flow information to be established and / or the source Qos Flow information to be established is contained in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity. The destination Qos Flow information to be established contains one or more Qos Flows mapped to the DRB at the destination. The source Qos Flow information to be established contains one or more Qos Flows mapped to the DRB at the source. If the DRB information to be established contains only the destination Qos Flow information to be established, it means that the DRB is only used to process new data from the core network, and the corresponding DRB is not used at the source. If the DRB information to be established contains only the source Qos Flow information to be established, it means that the DRB is only used to process data forwarded from the source base station, and the corresponding DRB is not used at the destination. The destination base station central unit user plane entity can release the DRB after receiving the end marker packet.

[0347] The destination Qos Flow information to be established can be represented by the existing Qos Flow information to be established in the DRB information to be established in the interface message between the base station central unit control plane entity and the base station central unit user plane entity. In this case, a new information element (IE) needs to be defined, such as the source Qos Flow information to be established or the old Qos Flow information to be established, to represent the mapping information at the source or the source Qos Flow information to be established. The existing Qos Flow information to be established in the DRB information to be established is a mandatory field. In order to represent a DRB that is an old DRB at the source and not used at the destination, only the source Qos Flow information to be established or the old Qos Flow information to be established, i.e. the information of the Qos Flows mapped to the DRB at the source, needs to be contained in the DRB information to be established. In order to handle this case, the specific method and steps are the same as in step 1502, which will not be described here.

[0348] The source end to be established Qos flow information can be represented by the existing to be established Qos Flow information in the DRB to be established information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and a new information element (IE) such as the destination to be established Qos flow information or the new to be established Qos flow information is needed to represent the mapping information of the destination end or the destination to be established Qos flow information. The existing to be established Qos Flow information in the DRB to be established information is a mandatory field, and in order to represent that a certain DRB is the DRB of the destination end, the destination to be established Qos flow information or the new to be established Qos flow information, i.e. the information of the Qos flow of the destination end mapped to the DRB, is only needed to be contained in the to be established DRB information, and in order to handle this case, the specific method is the same as in step 1502, and thus will not be described here.

[0349] The destination end flow mapping information and / or the source end flow mapping information is contained in the to be modified DRB information sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity. The destination end flow mapping information contains one or more Qos flows mapped to the DRB at the destination end. The source end flow mapping information contains one or more Qos flows mapped to the DRB at the source end. If only the destination end flow mapping information is contained in the to be modified DRB information, it means that the DRB is only used to process new data from the core network, and the corresponding DRB is not used at the source end. If only the source end flow mapping information is contained in the to be modified DRB information, it means that the DRB is only used to process data forwarded from the source base station, and the corresponding DRB is not used at the destination end. The destination base station central unit user plane entity can release the DRB after receiving the end marker packet.

[0350] The Qos flow(s) mapped to the DRB at the destination end can be represented by the existing flow mapping information in the to be modified DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and a new information element (IE) such as the source flow mapping information or the old flow mapping information is needed to represent the Qos flow(s) mapped to the DRB at the source end.

[0351] The Qos flow(s) mapped to the DRB at the source end can be represented by the existing flow mapping information in the to be modified DRB information in the interface message between the base station central unit control plane entity and the base station central unit user plane entity, and a new information element (IE) such as the destination flow mapping information or the new flow mapping information is needed to represent the Qos flow(s) mapped to the DRB at the destination end.

[0352] The destination base station central unit control plane entity can send the above information to the destination base station central unit user plane entity using a bearer context establishment request, a bearer context modification request message, or other messages. The DRB to be established is either a DRB included in the PDU session resource establishment list in the bearer context establishment request message or a DRB included in the PDU session resource establishment list (also called the PDU session resource establishment modification list) in the bearer context modification request message. For EN-DC to SA handover where the source and destination base stations are shared, the destination base station central unit control plane entity can send the above information to the destination base station central unit user plane entity via the DRB to be established in the bearer context modification request message.

[0353] This concludes the description of the handover support method 1600 of the present invention. This method ensures correct processing between the control plane and user plane of the destination base station central unit, even when the destination base station uses a different QoS flow to DRB mapping than the source base station. This avoids data loss, improves data transmission efficiency, and enhances the reliability of data forwarding during handover.

[0354] Figure 17 This is an exemplary flowchart illustrating a method 1700 for supporting handover according to an embodiment of the present invention. The method 1700 can be used for intra-system handover or inter-system handover, and can be executed on the user plane entity side of the source base station central unit. The method includes the following steps.

[0355] like Figure 17 As shown, in method 1700, in step S1701, source-end DRB configuration information and destination-end DRB configuration information are received from the destination base station central unit control plane entity. And / or, the mapping of source-end QoS flow to data radio bearer DRB and the mapping of destination-end QoS flow to DRB are received from the destination base station central unit control plane entity.

[0356] In step S1702, the forwarded data received from the source base station is processed using the source DRB configuration and / or the source QoS flow to DRB mapping, and the new data received from the core network is processed using the destination DRB configuration and / or the destination QoS flow to DRB mapping.

[0357] The similarities between Method 1700 and Methods 1500 and 1600 will not be repeated here.

[0358] So far, the description of the method 1700 for supporting handover according to the present application is completed. Through the method, in the case that the destination base station adopts different Qos flow to DRB mapping from the source base station, the destination base station central unit control plane and the destination base station central unit user plane can be ensured to have correct processing, data loss can be avoided, the efficiency of data transmission can be improved, and the reliability of data forwarding in handover can be improved.

[0359] Figure 18 An exemplary flow chart of a method 1800 for supporting handover according to an embodiment of the present application is shown. The method 1800 can be used for intra-system handover or inter-system handover. The method comprises the following steps.

[0360] In step S1801, the destination base station central unit control plane entity receives a handover request message from the source base station or from the core network. The handover request message received from the source base station is an inter-base station interface application layer message, such as an XnAP message. The handover request message received from the core network is an application layer message of the interface between the base station and the core network, such as an NGAP message. The handover request message contains configuration information of the UE at the source base station end, and the configuration information contains DRB configuration information and / or Qos flow to DRB mapping.

[0361] The destination base station central unit control plane entity decides the DRB configuration information and / or Qos flow to DRB mapping at the destination end.

[0362] The destination base station central unit control plane entity can decide to use the same DRB configuration as the source end or different DRB configuration.

[0363] If the destination base station central unit control plane entity decides to use the same DRB configuration and the same Qos flow to DRB mapping as the source base station, the information is sent to the destination base station central unit user plane entity through the DRB to be established and the Qos flow information to be established on the DRB. The destination base station central unit control plane entity sends the information to the destination base station central unit user plane entity through a bearer context establishment request message. The destination base station central unit control plane entity sends the mapping relationship to the destination base station central unit user plane entity through the Qos flow(s) to be established contained in the DRB to be established in the bearer context establishment request message.

[0364] If the target base station central unit control plane entity decides to use the same Qos flow to DRB mapping as the source base station, it sends the mapping relationship to the target base station central unit user plane entity. The target base station central unit control plane entity sends the mapping relationship to the target base station central unit user plane entity through the bearer context setup request message. The target base station central unit control plane entity sends the mapping relationship to the target base station central unit user plane entity through the information of the Qos flow(s) to be established contained in the DRB to be established in the bearer context setup request message.

[0365] If the target base station central unit control plane entity decides to use different DRB configuration and / or different Qos flow to DRB mapping than the source base station, in order to ensure lossless during handover, the target base station central unit control plane entity temporarily configures the same DRB configuration and / or Qos flow to DRB mapping as the source base station for processing the data forwarded by the source base station. The target base station central unit control plane entity decides the target end DRB configuration and / or Qos flow to DRB mapping for the target base station central unit user plane entity to process the new data received from the core network.

[0366] There are two methods in the present application to inform the UE of the mapping relationship. One method is that the target base station central unit control plane entity directly contains the target end DRB configuration and / or Qos flow to DRB mapping in the handover command message, which is sent to the UE through the source base station. The other method is that the target base station central unit control plane entity contains the source end DRB configuration and / or Qos flow to DRB mapping in the handover command message, which is sent to the UE through the source base station. Then the target base station central unit control plane entity sends a radio resource control (RRC) reconfiguration message to the UE, which contains the target end decided DRB configuration and / or Qos flow to DRB mapping. When the target base station central unit user plane entity receives the end marker, the target base station central unit user plane entity sends an indication message to the target base station central unit control plane entity, and the target base station central unit control plane entity sends the target end decided DRB configuration and / or Qos flow to DRB mapping to the UE through the RRC reconfiguration message.

[0367] Step S1802, the destination base station central unit control plane entity sends the source DRB configuration and / or the mapping of Qos Flow to DRB to the destination base station central unit user plane entity. The Qos flow information to be established contained in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity is set according to the source Qos flow to DRB mapping. The configuration of the DRB to be established is the source configuration. The destination base station central unit control plane entity can send the information to the destination base station central unit user plane entity through a bearer context establishment request message or other messages.

[0368] Step S1803, the destination base station central unit user plane entity receives the information from the destination base station central unit control plane entity in step S1802. The destination base station central unit user plane entity saves the received information.

[0369] For the DRB corresponding to the request data forwarding, the destination base station central unit user plane entity allocates channel information for data forwarding and sends it to the destination base station central unit control plane entity.

[0370] There are two methods for the interaction between the destination base station central unit control plane entity and the gNB-DU:

[0371] Method one, the destination base station central unit control plane entity sends a UE context establishment request message to the destination base station distribution unit (hereinafter referred to as gNB-DU). The message contains the configuration of the source DRB. Corresponding to the source DRB, the DRB to be established contains the Qos flow(s) mapped to the DRB in the source. If the destination uses the same DRB configuration and the same Qos flow to DRB mapping as the source, the DRB to be established contains the Qos flow(s) mapped to the DRB. If the destination uses the same DRB configuration as the source and different Qos flow to DRB mapping, the DRB to be established can contain the Qos flow(s) mapped to the DRB in the source. The gNB-DU allocates a downlink transport layer address and a channel identifier for each DRB to be established. The gNB-DU sends a UE context establishment response message to the destination base station central unit control plane entity, which contains the downlink transport layer address and channel identifier allocated by the gNB-DU for each DRB. The base station central unit control plane entity sends the downlink transport layer address and channel identifier allocated by the gNB-DU for each DRB to the destination base station central unit user plane entity.

[0372] Method two, the destination base station central unit control plane entity sends a UE context setup request message to the destination base station distributed unit (hereinafter referred to as gNB-DU). The message contains the configuration of the source end DRB and the DRB configuration decided at the destination end. Corresponding to the source end DRB, the DRB to be established contains the Qos flow(s) mapped to the DRB at the source end. Corresponding to the new DRB decided at the destination end, the DRB to be established contains the Qos flow(s) mapped to the DRB decided by the destination base station central unit control plane entity. If the destination end uses the same DRB configuration and the same Qos flow to DRB mapping as the source end, the DRB to be established contains the Qos flow(s) mapped to the DRB. If the destination end uses the same DRB configuration as the source end and different Qos flow to DRB mapping, the DRB to be established can contain the Qos flow(s) mapped to the DRB at the source end and / or the Qos flow(s) mapped to the DRB at the destination end. The gNB-DU allocates a downlink transport layer address and a tunnel identifier for each DRB to be established. The gNB-DU sends a UE context setup response message to the destination base station central unit control plane entity, which contains the downlink transport layer address and the tunnel identifier allocated by the gNB-DU for each DRB. The base station central unit control plane entity sends the downlink transport layer address and the tunnel identifier allocated by the gNB-DU for each DRB to the destination base station central unit user plane entity. The destination base station central unit user plane entity receives the forwarded data from the source base station, and the destination base station central unit user plane entity processes the forwarded data received from the source base station using the received Qos flow to DRB mapping.

[0373] After the destination base station receives the end marker, it can send an indication message to the destination base station central unit control plane entity that the forwarding of data is complete.

[0374] Step S1804, the destination base station central unit control plane entity sends the destination end DRB configuration and / or the destination end Qos flow to DRB mapping to the destination base station central unit user plane entity.

[0375] The Qos flow information to be established in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity contains the mapping of the destination end Qos flow to DRB, which is set according to the mapping of the destination end Qos flow to DRB. The configuration of the DRB to be established is the configuration of the destination end. The destination end flow mapping information is contained in the DRB information to be modified sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity. The destination end flow mapping information contains one or more Qos flows mapped to the DRB at the destination end. The destination base station central unit control plane entity can send the information to the destination base station central unit user plane entity through a bearer context modification request or a bearer context establishment request message or other messages.

[0376] The method for sending the indication information of the end of forwarding data to the destination base station central unit control plane entity after the destination base station central unit user plane entity receives the end marker, the destination base station central unit control plane entity sends the configuration of the destination end DRB and / or the mapping of the destination Qos flow to DRB to the destination base station central unit user plane entity. The destination base station central unit control plane entity sends an RRC reconfiguration message to the UE, and sends the configuration of the DRB decided by the destination end and / or the mapping of the Qos flow to DRB to the UE.

[0377] The destination base station central unit user plane entity deletes the DRB information used at the source end but not used at the destination end.

[0378] Corresponding to the interaction method one between the destination base station central unit control plane entity and the gNB-DU, the destination base station central unit control plane entity sends a UE context modification request message to the destination gNB-DU. The message contains the DRB configuration decided at the destination. Corresponding to the new DRB decided at the destination, the to-be-established DRB contains the Qos flow(s) decided by the destination base station central unit control plane entity and mapped to the DRB. If the destination uses the same DRB configuration as the source and different Qos flow-to-DRB mapping, the to-be-modified DRB can contain the Qos flow(s) mapped to the DRB by the destination. The gNB-DU allocates a downlink transport layer address and a tunnel identifier for each to-be-established DRB. The gNB-DU releases the old DRB configuration, which is the DRB of the source and the source configuration is for processing the forwarded data. The gNB-DU sends a UE context modification response message to the destination base station central unit control plane entity, which contains the downlink transport layer address and the tunnel identifier allocated by the gNB-DU for each DRB. The base station central unit control plane entity sends the downlink transport layer address and the tunnel identifier allocated by the gNB-DU for each DRB to the destination base station central unit user plane entity.

[0379] Corresponding to the interaction method two between the destination base station central unit control plane entity and the gNB-DU, the release process of the old DRB on the gNB-DU is as described in the method or according to the following method. The old DRB is the DRB of the source and the source configuration is for processing the forwarded data. Figure 23

[0380] If no new data is received on a DRB within a certain time, the gNB-DU sends a UE context modification required message to the destination base station central unit control plane entity. The message contains the identifier of the DRB that needs to be released. The destination base station central unit control plane entity can release the old DRB after receiving the message.

[0381] In step S1805, the destination base station central unit user plane entity receives the information from the destination base station central unit control plane entity in step S1804, and the destination base station central unit user plane uses the newly received Qos flow-to-DRB mapping to process the new data received from the core network and sends it to the UE through the gNB-DU.

[0382] ​So far, the description of the method 1800 for supporting handover of the present application is completed. Through the method, in the case that the target base station adopts different DRB configurations and / or different Qos flow to DRB mappings from the source base station, the target base station central unit control plane and the target base station central unit user plane and gNB-DU can be ensured to have correct processing, data loss can be avoided, the efficiency of data transmission can be improved, and the reliability of data forwarding in handover can be improved.

[0383] Figure 19 is an exemplary flowchart illustrating a method 1900 for supporting handover according to an embodiment of the present application. The method 1900 can be used for intra-system handover or inter-system handover, and can be executed at the side of a target base station central unit control plane entity. The method includes the following steps.

[0384] As shown in Figure 19 , in the method 1900, at step S1901, a handover request message from a source base station or from a core network is received.

[0385] At step S1902, a source quality of service (Qos) flow to data radio bearer (DRB) mapping is sent to a target base station central unit user plane entity, wherein the target base station central unit user plane entity uses the received source Qos flow to DRB mapping to process forwarded data received from the source base station.

[0386] At step S1903, a target Qos flow to DRB mapping is sent to the base station central unit user plane entity, wherein the target base station central unit user plane uses the newly received Qos flow to DRB mapping to process new data received from the core network and sent to a user equipment (UE).

[0387] The method 1900 is similar to the method 1800, and the repeated parts will not be described again.

[0388] So far, the description of the method 1900 for supporting handover of the present application is completed. Through the method, in the case that the target base station adopts different Qos flow to DRB mappings from the source base station, the target base station central unit control plane and the target base station central unit user plane can be ensured to have correct processing, data loss can be avoided, the efficiency of data transmission can be improved, and the reliability of data forwarding in handover can be improved.

[0389] Figure 20 is an exemplary flowchart illustrating a method 2000 for supporting handover according to an embodiment of the present application. The method 2000 can be used for intra-system handover or inter-system handover, and can be executed at the side of a target base station central unit user plane entity. The method includes the following steps.

[0390] As shown in Figure 20As shown, in the method 2000, in step S2001, the mapping of source QoS flow to data radio bearer (DRB) is received from the destination base station central unit control plane entity.

[0391] In step S2002, the received mapping of source QoS flow to DRB is used to process the forwarded data received from the source base station.

[0392] In step S2003, the mapping of destination QoS flow to DRB is received from the destination base station central unit control plane entity.

[0393] In step S2004, the newly received mapping of QoS flow to DRB is used to process the new data received from the core network and sent to the user equipment (UE).

[0394] The method 2000 is similar to the method 1800 and the method 1900, and the repeated parts are not described again.

[0395] So far, the description of the method 2000 for supporting handover according to the present application is completed. Through the method, in the case that the destination base station adopts different QoS flow to DRB mapping from the source base station, the destination base station central unit control plane and the destination base station central unit user plane can be correctly processed, data loss can be avoided, the efficiency of data transmission can be improved, and the reliability of data forwarding in handover can be improved.

[0396] Figure 21 An exemplary flowchart of a method 2100 for supporting handover according to an embodiment of the present application is shown. The method 2100 can be used for intra-system handover or inter-system handover. The method includes the following steps.

[0397] In step S2101, the destination base station central unit control plane entity receives a handover request message from the source base station or from the core network. The handover request message received from the source base station is an inter-base station interface application layer message, such as an XnAP message. The handover request message received from the core network is an application layer message of the interface between the base station and the core network, such as an NGAP message. The handover request message contains configuration information of the UE at the source base station end, and the configuration information contains DRB configuration information and / or QoS flow to DRB mapping.

[0398] The destination base station central unit control plane entity decides the DRB configuration information and / or QoS flow to DRB mapping at the destination end.

[0399] There are two methods for notifying the UE of the mapping relationship in the present application. One method is that the destination base station central unit control plane entity directly contains the destination DRB configuration information and / or the destination Qos flow to DRB mapping in the handover command message, which is sent to the UE through the source base station. Another method is that the destination base station central unit control plane entity contains the source DRB configuration information and / or the source Qos flow to DRB mapping in the handover command message, which is sent to the UE through the source base station. Then the destination base station central unit control plane entity sends a radio resource control (RRC) reconfiguration message to the UE, which contains the destination determined DRB configuration information and / or the destination Qos flow to DRB mapping. The destination base station central unit control plane entity can decide when to send the RRC reconfiguration message to the UE according to the implementation.

[0400] Step S2102 is the same as step S1802, which will not be repeated here.

[0401] In step S2103, the destination base station central unit user plane entity receives the information from the destination base station central unit control plane entity. The destination base station central unit user plane entity saves the received information.

[0402] For the DRB corresponding to the request data forwarding, the destination base station central unit user plane entity allocates the channel information for data forwarding and sends it to the destination base station central unit control plane entity.

[0403] The interaction method between the destination base station central unit control plane entity and the gNB-DU is the same as described in step 1803, which will not be repeated here.

[0404] The destination base station central unit user plane entity receives the data forwarded from the source base station, and the destination base station central unit user plane entity processes the forwarded data from the source base station using the received mapping.

[0405] In step S2104, the destination base station central unit control plane entity sends the destination DRB configuration and / or the destination Qos flow to DRB mapping to the destination base station central unit user plane entity and sends the indication information.

[0406] The DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity includes QoS flow information to be established. The QoS flow information to be established in the DRB information is set according to the mapping from the destination QoS flow to the DRB. The DRB information to be modified sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity includes destination flow mapping information. The destination flow mapping information includes one or more QoS flows mapped from the destination to the DRB. The destination base station central unit control plane entity can send this information to the destination base station central unit user plane entity via a bearer context modification request, a bearer context establishment request message, or other messages.

[0407] The destination base station central unit control plane entity sends an RRC reconfiguration message to the UE, sending the destination-determined DRB configuration and / or QoS Flow to DRB mapping to the UE.

[0408] In step S2105, the destination base station central unit user plane entity receives the information from the destination base station central unit control plane entity in step S2104. The destination base station central unit user plane entity does not delete the old mapping relationships at the source end, nor does it delete the DRBs temporarily used at the source end for processing forwarded data but not at the destination end. Based on the received instruction information, the destination base station central unit user plane entity does not delete the old mapping relationships at the source end and / or does not delete the DRBs temporarily used for processing forwarded data but not at the destination end. The destination base station central unit user plane entity processes the data forwarded from the source base station using the previously received mapping from the source end QoS flow to the DRB.

[0409] After receiving the end marker, the destination base station central unit user plane entity deletes the old mapping relationships at the source end and / or deletes DRBs temporarily used for processing forwarded data but not used at the destination end. The destination base station central unit user plane entity processes the new data received from the core network using the newly received QoS flow to DRB mapping. The destination base station central unit user plane entity transmits the data received from the core network to the UE via gNB-DU.

[0410] The release process of the old DRB on the gNB-DU is as follows: Figure 25 The method described or as follows. The old DRB is the source-side DRB, configured to handle forwarded data.

[0411] If no new data is received on a DRB within a certain period of time, the gNB-DU sends a UE context modification request message to the destination base station central unit control plane entity. This message contains an identifier indicating that the DRB needs to be released. Upon receiving this message, the destination base station central unit control plane entity can release the old DRB.

[0412] This concludes the description of the handover support method 2100 of the present invention. This method ensures correct processing of the target base station central unit control plane, target base station central unit user plane, and gNB-DU, even when the target base station uses a different DRB configuration and / or a different QoS flow to DRB mapping than the source base station. This avoids data loss, improves data transmission efficiency, and enhances the reliability of data forwarding during handover.

[0413] Figure 22 This is an exemplary flowchart illustrating a method 2200 for supporting handover according to an embodiment of the present invention. The method 2200 can be used for intra-system handover or inter-system handover, and can be executed on the control plane entity side of the destination base station central unit. The method includes the following steps.

[0414] like Figure 22 As shown, in method 2200, in step S2201, a handover request message is received from the source base station or the core network.

[0415] In step S2202, the source QoS Flow mapping to the DRB is sent to the destination base station central unit user plane entity, wherein the destination base station central unit user plane entity uses the received mapping to process the forwarded data received from the source base station.

[0416] In step S2203, the destination QoS flow to DRB mapping is sent to the destination base station central unit user plane entity and indication information is sent. The base station central unit user plane entity uses the newly received destination QoS flow to DRB mapping to process the new data received from the core network.

[0417] Method 2200 is similar to Method 2100, and the repetitions will not be repeated.

[0418] This concludes the description of the handover support method 2200 of the present invention. This method ensures correct processing between the control plane and user plane of the destination base station central unit, even when the destination base station uses a different QoS flow to DRB mapping than the source base station. This avoids data loss, improves data transmission efficiency, and enhances the reliability of data forwarding during handover.

[0419] Figure 23is an exemplary flow chart illustrating a method 2300 for supporting handover according to an embodiment of the present application. The method 2300 can be used for intra-system handover or inter-system handover, and can be performed at a target base station central unit user plane entity side. The method comprises the following steps.

[0420] As shown in Figure 23 In the method 2300, at step S2301, the mapping of source Qos flow to data radio bearer (DRB) is received from a target base station central unit control plane entity.

[0421] At step S2302, the forwarding data received from the source base station is processed using the received mapping of source Qos flow to DRB.

[0422] At step S2303, the mapping of target Qos flow to DRB and indication information is received from the target base station central unit control plane entity.

[0423] At step S2304, the new data received from the core network is processed using the newly received mapping of target Qos flow to DRB, wherein the old mapping relationship at the source side and / or the DRB temporarily used for processing the forwarding data but not used at the target side is not deleted according to the received indication information.

[0424] The method 2300 is similar to the method 2100 and the method 2200, and the repeated parts will not be described again.

[0425] So far, the description of the method 2300 for supporting handover according to the present application is completed. Through the method, in the case that the target base station uses different Qos flow to DRB mapping from the source base station, the target base station central unit control plane and the target base station central unit user plane can be ensured to have correct processing, data loss can be avoided, the efficiency of data transmission can be improved, and the reliability of data forwarding in handover can be improved.

[0426] Figure 24 is an exemplary flow chart illustrating a method 2400 for supporting handover according to an embodiment of the present application. The method 2400 can be used for intra-system handover or inter-system handover. The method comprises the following steps.

[0427] At step S2401, a target base station central unit control plane entity receives a handover request message from a source base station or from a core network. The handover request message received from the source base station is an inter-base station interface application layer message such as an XnAP message. The handover request message received from the core network is an application layer message of a base station and core network interface, for example, an NGAP message. The handover request message contains configuration information of a UE at the source base station side, and the configuration information contains DRB configuration information and / or Qos flow to DRB mapping.

[0428] The destination base station central unit control plane entity decides the destination DRB configuration information and / or the mapping of Qos Flow to DRB.

[0429] There are two methods in the present application to inform the UE of the mapping relationship. One method is that the destination base station central unit control plane entity directly includes the destination DRB configuration information and / or the mapping of destination Qos Flow to DRB in the handover command message, which is sent to the UE by the source base station. Another method is that the destination base station central unit control plane entity includes the source DRB configuration information and / or the mapping of source Qos Flow to DRB in the handover command message, which is sent to the UE by the source base station. Then the destination base station central unit control plane entity sends a radio resource control (RRC) reconfiguration message to the UE, which includes the destination decided DRB configuration information and / or the mapping of destination Qos Flow to DRB. The destination base station central unit control plane entity can decide when to send the RRC reconfiguration message to the UE according to the implementation.

[0430] Step S2402 is the same as step S1802, which will not be repeated here.

[0431] In step S2403, the destination base station central unit user plane entity receives the information from the destination base station central unit control plane entity. The destination base station central unit user plane entity saves the received information.

[0432] For the DRB corresponding to the request data forwarding, the destination base station central unit user plane entity allocates the channel information for data forwarding and sends it to the destination base station central unit control plane entity.

[0433] The interaction method between the destination base station central unit control plane entity and the gNB-DU is the same as described in step S1803, which will not be repeated here.

[0434] The destination base station central unit user plane entity receives the data forwarded from the source base station, and the destination base station central unit user plane entity processes the forwarded data from the source base station using the received mapping.

[0435] In step S2404, the destination base station central unit control plane entity sends the destination DRB configuration and / or the mapping of destination Qos flow to DRB to the destination base station central unit user plane entity.

[0436] The Qos flow information to be established included in the DRB information to be established sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity is set according to the mapping of the destination end Qos flow to DRB. The destination end flow mapping information is included in the DRB information to be modified sent by the destination base station central unit control plane entity to the destination base station central unit user plane entity. The destination end flow mapping information includes one or more Qos flows mapped to the DRB at the destination end. The destination base station central unit control plane entity can send the information to the destination base station central unit user plane entity through a bearer context modification request or a bearer context establishment request message or other messages.

[0437] The destination base station central unit control plane entity sends an RRC reconfiguration message to the UE, and sends the DRB configuration decided by the destination end and / or the mapping of the Qos Flow to DRB to the UE.

[0438] In step S2405, the destination base station central unit user plane entity receives the information in step S2404 from the destination base station central unit control plane entity, and the destination base station central unit user plane entity does not delete the old mapping relationship at the source end, and the destination base station central unit user plane entity does not delete the DRB temporarily used for processing the forwarded data at the source end and not used at the destination end. The destination base station central unit user plane entity processes the data received from the source base station using the previously received mapping of the Qos flow to DRB at the source end.

[0439] After the destination base station central unit user plane entity receives the end marker, the destination base station central unit user plane entity deletes the old mapping relationship at the source end and / or deletes the DRB temporarily used for processing the forwarded data at the destination end. The destination base station central unit user plane entity processes the new data received from the core network using the newly received DRB configuration and / or the mapping of the Qos flow to DRB. The destination base station central unit user plane entity sends the data received from the core network to the UE through the gNB-DU.

[0440] The release process of the old DRB on the gNB-DU is as described in the method or according to the following method. The old DRB is the DRB at the source end, and the destination end configuration is for processing the forwarded data. Figure 25

[0441] No new data is received on a DRB within a certain time, and the gNB-DU sends a UE context modification required message to the destination base station central unit control plane entity. The message includes the identification of the DRB required to be released. The destination base station central unit control plane entity can release the old DRB after receiving the message. ​

[0442] So far, the description of the method 2400 for supporting handover according to the present application is completed. Through the method, the target base station central unit control plane, the target base station central unit user plane and the gNB-DU can be ensured to have correct processing in the case that the target base station adopts different DRB configurations and / or different Qos flow to DRB mappings from the source base station, data loss is avoided, the efficiency of data transmission is improved, and the reliability of data forwarding in handover is improved.

[0443] Figure 25 An exemplary flow chart of a method 2500 for supporting handover according to an embodiment of the present application is shown. The method 2500 can be used for inter-system handover or intra-system handover. The method comprises the following steps.

[0444] In step S2501, the target base station central unit user plane entity receives the data forwarding end marker data packet.

[0445] In step S2502, the target base station central unit user plane entity sends the data forwarding end indication information to the target base station central unit control plane entity. The target base station central unit user plane entity can send the data forwarding end indication information to the target base station central unit control plane entity after receiving the end marker data packet of all the data forwarding DRBs.

[0446] In step S2503, the target base station central unit control plane entity receives the data forwarding end indication information. The target base station central unit control plane entity sends a message to the target gNB-DU to request to release the old DRB. The old DRB is the DRB at the source end, which is configured to process the forwarded data. The target base station central unit control plane entity can request the gNB-DU to release the old DRB through a UE context modification message or other message.

[0447] The gNB-DU receives the information from the target base station central unit control plane entity. The gNB-DU releases the old DRB. The gNB-DU sends a response message to the target base station central unit control plane entity.

[0448] So far, the description of the method 2500 for supporting handover according to the present application is completed. Through the method, the gNB-DU can timely release the unnecessary DRB, save the wireless resources, and improve the capacity of the system or the ability to serve more users.

[0449] Figure 26 An exemplary flow chart of a method 2600 for supporting handover according to an embodiment of the present application is shown. The method 2600 can be used for inter-system handover or intra-system handover, and can be executed at the side of the target base station central unit control plane entity. The method comprises the following steps.

[0450] At step S2601, the source base station central unit control plane entity receives the handover command message.

[0451] The handover command message contains the E-RAB identification for data forwarding and data forwarding tunnel information. In the PDU session establishment procedure, the source base station central unit control plane entity receives from the core network the information of the PDU session to be established, one or more Qos flows in the PDU session and the E-RAB identification mapped to the Qos flows, and the source base station central unit control plane entity saves the E-RAB identification mapped to the Qos flows.

[0452] At step S2602, the source base station central unit control plane entity sends the bearer context modification request message to the source base station central unit user plane entity.

[0453] The message contains the data forwarding information for handover to E-UTRAN or inter-system handover data forwarding information. The information (i.e., data forwarding information for handover to E-UTRAN or inter-system handover data forwarding information) element can also be other names or otherwise named without departing from the scope of the present application, and the purpose of the information element is to inform the source base station central unit user plane entity of the data forwarding information. The data forwarding information contains downlink data forwarding information. The downlink data forwarding information contains a transport layer address and a tunnel identification. The downlink data forwarding information also contains a list of Qos flows for which data is forwarded over the data forwarding tunnel. The transport layer address and tunnel identification are the data forwarding tunnel information for each E-RAB assigned by the target base station received by the source base station central unit control plane entity in the handover command message. The source base station central unit control plane entity receives from the core network in the PDU session establishment procedure the E-RAB identification mapped to each Qos flow, so the source base station central unit control plane entity knows the Qos flow(s) for which data is forwarded over each E-RAB tunnel. The downlink data forwarding information can also contain DRB identification. For inter-system handover, the DRB identification corresponds to each E-RAB identification, and can be the same as or one-to-one corresponding to the E-RAB identification. The downlink data forwarding information can also contain E-RAB identification.

[0454] At step S2603, the source base station central unit user plane entity receives the message from the source base station central unit control plane entity. The source base station central unit user plane entity saves the information in the received message. The source base station central unit user plane entity forwards data according to the received information. The information is, for example, data forwarding information for handover to E-UTRAN or inter-system handover data forwarding information.

[0455] The source base station forwards the data of each Qos flow through the corresponding channel. The source base station central unit user plane entity knows that it is an inter-system handover according to the new information element contained in the received message, and switches to the data forwarding information of the E-UTRAN or the inter-system handover data forwarding information, so that the SDAP packet header is not contained in the forwarded data packet. The source base station central unit user plane entity forwards the PDCP SDU without the SDAP packet header.

[0456] For intra-system handover, the data packet, i.e. PDCP SDU, forwarded by the source base station central unit user plane entity on the channel corresponding to each DRB can contain the SDAP packet header.

[0457] So far, the description of the method 2600 for supporting handover according to the present application is completed. Through the method, the source base station central unit user plane entity can correctly forward data to the target base station in the case that the number of E-RABs used by the target base station and the number of DRBs used by the source NG-RAN are different, the source base station central unit user plane entity can forward the data packet of the Qos flow to the correct E-RAB channel, the source base station central unit user plane entity can forward the data packet without the SDAP packet header for inter-system handover, avoid affecting the target E-UTRAN base station, and ensure sending the correct data packet, avoid data loss, improve the efficiency of data transmission, and improve the reliability of data forwarding in handover.

[0458] Figure 27 An exemplary flowchart of a method 2700 for supporting handover according to an embodiment of the present application is shown. The method 2700 can be used for inter-system handover or intra-system handover, and can be executed on the side of the target base station central unit control plane entity. The method includes the following steps.

[0459] In step S2701, the source base station central unit control plane entity receives a handover command message.

[0460] The handover command message contains E-RAB identification and data forwarding channel information for data forwarding. In the PDU session establishment process, the source base station central unit control plane entity receives from the core network the information of the PDU session to be established, one or more Qos flows in the PDU session, and the E-RAB identification mapped by the Qos flow, and the source base station control plane entity saves the E-RAB identification mapped by the Qos flow.

[0461] In step S2702, the source base station central unit control plane entity sends a bearer context modification request message to the source base station central unit user plane entity. The source base station central unit control plane entity informs the source base station central unit user plane entity of the data forwarding tunnel information and the Qos flow information to be forwarded on each tunnel through the DRB information to be established and / or the DRB information to be modified in the message.

[0462] The source base station central unit control plane entity informs the source base station central unit user plane entity of the data forwarding tunnel information and the Qos flow information to be forwarded on each tunnel through the DRB information to be established and / or the DRB information to be modified in the PDU session resource modification item in the message.

[0463] If the DRB at the source base station central unit user plane entity has been configured in the PDU session establishment procedure, the source base station central unit control plane entity sends the transport layer address and the tunnel identity allocated by the target base station through the DRB data forwarding information in the DRB modification item, and sends the Qos flow(s) to be forwarded on the tunnel corresponding to the DRB through the flow mapping information in the DRB modification item. The DRB modification item contains the DRB identity.

[0464] For the case that the number of E-RABs of the target base station is more than the number of DRBs of the source, the DRB at the source base station central unit user plane entity has not been configured in the PDU session establishment procedure, the source base station central unit control plane entity sends the transport layer address and the tunnel identity allocated by the target base station to the source base station central unit user plane entity through the DRB data forwarding information in the DRB establishment item, and sends the Qos flow(s) to be forwarded on the tunnel corresponding to the DRB to the source base station central unit user plane entity through the Qos flow information to be established in the DRB establishment item. The DRB establishment item contains the DRB identity.

[0465] For the inter-system handover, the DRB identity corresponds to each E-RAB identity, and can be the same as the E-RAB identity or one-to-one correspondence with the E-RAB identity. The bearer context modification request message further contains indication information of the inter-system handover. The indication information of the inter-system handover can be contained in the PDU session resource modification information or the DRB information to be modified or the DRB information to be established.

[0466] The data forwarding information includes downlink data forwarding information. The downlink data forwarding information includes a transport layer address and a tunnel identifier. The transport layer address and the tunnel identifier are data forwarding tunnel information for each E-RAB allocated by the target base station to the source base station central unit control plane entity in the handover command message. The source base station control plane entity receives the E-RAB identifier mapped by each Qos flow from the core network in the PDU session establishment process, so that the source base station control plane entity knows the Qos flow(s) forwarded through each E-RAB tunnel.

[0467] In step S2703, the source base station central unit user plane entity receives the message from the source base station central unit control plane entity. The source base station central unit user plane entity saves the received information. The source base station central unit user plane entity forwards data according to the received information.

[0468] The source base station central unit user plane entity knows the Qos flow(s) forwarded through the tunnel according to the DRB data forwarding information and the flow mapping information of each DRB in the received DRB information to be modified. Alternatively, the source base station central unit user plane entity knows the Qos flow(s) forwarded through the tunnel according to the DRB data forwarding information of each DRB in the received DRB information to be established and the Qos flow information to be established.

[0469] The source base station forwards the data of each Qos flow through the corresponding tunnel. For inter-system handover, the source base station central unit user plane entity knows it is inter-system handover according to the received indication information of inter-system handover, so that the SDAP packet header is not included in the forwarded data packet. The source base station central unit user plane entity forwards PDCP SDU without SDAP packet header. For intra-system handover, the PDCP SDU forwarded by the source base station central unit user plane entity on the tunnel corresponding to each DRB can include the SDAP packet header.

[0470] So far, the description of the method 2700 for supporting handover of the present application is completed. Through the method, the source base station central unit user plane entity can correctly forward data to the target base station in the case that the number of E-RABs used by the target base station is different from the number of DRBs used by the source NG-RAN, the source base station central unit user plane entity can forward the data packet of the Qos flow to the correct E-RAB tunnel, the source base station central unit user plane entity can forward the data packet without SDAP packet header for inter-system handover, avoid affecting the target E-UTRAN base station, and ensure sending correct data packet, avoid data loss, improve the efficiency of data transmission, and improve the reliability of data forwarding in handover.

[0471] Figure 28An exemplary flow chart illustrating a method 2800 for supporting handover according to an embodiment of the present application is shown. The method 2800 can be used for inter-system handover or intra-system handover, and can be performed at the side of a target base station central unit user plane entity. The method comprises the following steps.

[0472] At step S2801, the source base station central unit user plane entity receives a bearer context modification request message from a source base station central unit control plane entity.

[0473] At step S2802, the source base station central unit user plane entity forwards data according to the information in the received bearer context modification request message.

[0474] The method 2800 is similar to the method 2600, and the repeated parts will not be described again.

[0475] So far, the description of the method 2800 for supporting handover according to the present application is completed. Through the method, the source base station central unit user plane entity can correctly forward data to the target base station when the number of E-RABs used by the target base station and the number of DRBs used by the source NG-RAN are different, the source base station central unit user plane entity can forward data packets of Qos flows to the correct E-RAB channel, the source base station central unit user plane entity can forward data packets without SDAP packet headers for inter-system handover, avoid affecting the target E-UTRAN base station, and ensure that the correct data packets are sent, avoid data loss, improve the efficiency of data transmission, and improve the reliability of data forwarding during handover.

[0476] Figure 29 An exemplary flow chart illustrating a method 2900 for supporting handover according to an embodiment of the present application is shown. The method 2900 can be used for inter-system handover or intra-system handover, and can be performed at the side of a target base station central unit user plane entity. The method comprises the following steps.

[0477] At step S2901, the source base station central unit user plane entity receives a bearer context modification request message from a source base station central unit control plane entity, wherein the data forwarding channel information and the quality of service guarantee Qos flow information forwarded on each channel are informed to the source base station central unit user plane entity through the data radio bearer DRB information to be established and / or the DRB information to be modified in the bearer context modification request message.

[0478] At step S2902, the source base station central unit user plane entity forwards data according to the information in the received bearer context modification request message.

[0479] The method 2900 is similar to the method 2700, and the repeated parts will not be described again.

[0480] Thus far, the description of the method 2900 for supporting handover according to the present application is completed. Through the method, in the case that the number of E-RABs used by the target base station and the number of DRBs used by the source NG-RAN are different, the source base station central unit user plane entity can correctly forward data to the target base station. The source base station central unit user plane entity can forward the data packets of the Qos flow to the correct E-RAB channel. The source base station central unit user plane entity can forward the data packets without SDAP packet header for inter-system handover, avoid affecting the target E-UTRAN base station, ensure sending correct data packets, avoid data loss, improve the efficiency of data transmission, and improve the reliability of data forwarding in handover.

[0481] The foregoing methods can be used alone or in combination to solve the problem of data forwarding in the process of intra-system or inter-system handover. Figures 3 to 29 The foregoing methods can be used alone or in combination to solve the problem of data forwarding in the process of intra-system or inter-system handover.

[0482] Figure 30 A schematic block diagram of an apparatus 3000 for supporting handover according to an embodiment of the present application is shown. The apparatus 3000 can be implemented on the side of a base station. For example, the apparatus 3000 can be implemented to perform one or more of the methods described above with reference to Figures 3 to 29 The foregoing methods can be used alone or in combination to solve the problem of data forwarding in the process of intra-system or inter-system handover.

[0483] As Figure 30 indicated, the apparatus 3000 can include a transceiver 3001, a processor 3002, and a memory 3003.

[0484] The transceiver 3001 transmits and receives signals. The memory 3003 stores instructions executable by the processor 3002, which, when executed by the processor 3002, cause the processor 3002 to perform one or more of the methods described above with reference to Figures 3 to 29 The foregoing methods can be used alone or in combination to solve the problem of data forwarding in the process of intra-system or inter-system handover.

[0485] According to embodiments of the present application, the foregoing method and apparatus for supporting handover can solve the problem of coordination between the source base station and the target base station in the handover process. In particular, in the case that the source base station and / or the target base station support separation of the control plane and the data plane, the source base station central unit control plane entity, the source base station central unit user plane entity, the target base station central unit control plane entity, and / or the target base station central unit user plane entity can work in full coordination. Data loss is reduced, data interruption time is reduced, useless data packets are avoided on the air interface, the efficiency of data forwarding is improved, and service continuity is ensured.

[0486] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method performed by a destination base station central unit user plane (CU-UP) in a wireless communication system, comprising: receiving, from a destination base station central unit control plane (CU-CP), a message for bearer context modification; identifying, based on the message not including packet data convergence protocol (PDCP) sequence number (SN) status information, PDCP service data units (SDUs) including PDCP SNs in received data packets; and discarding the PDCP SDUs including the PDCP SNs.

2. The method of claim 1, wherein, the message does not include the PDCP SN status information based on the handover involving full configuration.

3. The method of claim 1, wherein, identifying the PDCP SDUs including the PDCP SNs comprises: identifying PDCP SDUs attempted to be delivered by a source base station based on the PDCP SNs being present in the data packets.

4. The method of claim 1, wherein, the PDCP SDUs attempted to be delivered by the source base station are not transmitted to a user equipment (UE) by the destination base station CU-CP, and wherein the data packets comprise general packet radio service tunneling protocol user plane (GTP-U) data packets.

5. The method of claim 1, further comprising: receiving the data packets forwarded from a source base station CU-UP. 6.A method performed by a destination base station central unit control plane (CU-CP) in a wireless communication system, comprising: deciding whether a handover involves full configuration; generating a message for bearer context modification, the message not including packet data convergence protocol (PDCP) sequence number (SN) status information; and sending the message to a destination base station central unit user plane (CU-UP), wherein the message instructs the destination base station CU-UP to discard PDCP service data units (SDUs) including PDCP SNs in data packets forwarded from a source base station CU-UP. the message does not include the PDCP SN status information based on the handover involving full configuration.

7. The method of claim 6, wherein, the PDCP SDUs attempted to be delivered by the source base station are identified based on the PDCP SNs being present in the data packets.

8. The method of claim 6, wherein, the PDCP SDUs attempted to be delivered by the source base station are not transmitted to a user equipment (UE) by the destination base station CU-CP, and 9. The method of claim 6, wherein, wherein the data packets comprise general packet radio service tunneling protocol user plane (GTP-U) data packets. receiving a sequence number (SN) status transfer message.

10. The method of claim 6, further comprising: 11.An apparatus supporting handover, comprising: a transceiver that transmits and receives signals; a processor; and a memory storing instructions executable by the processor, the instructions, when executed by the processor, causing the processor to perform the method of any one of claims 1-10. ​ ​

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