WO2023083228A1 - 基站切换方法、基站和计算机可读存储介质 - Google Patents

基站切换方法、基站和计算机可读存储介质 Download PDF

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Publication number
WO2023083228A1
WO2023083228A1 PCT/CN2022/130975 CN2022130975W WO2023083228A1 WO 2023083228 A1 WO2023083228 A1 WO 2023083228A1 CN 2022130975 W CN2022130975 W CN 2022130975W WO 2023083228 A1 WO2023083228 A1 WO 2023083228A1
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Prior art keywords
base station
core network
identity
handover
handover request
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PCT/CN2022/130975
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English (en)
French (fr)
Inventor
姜冰心
费腾
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中兴通讯股份有限公司
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Publication of WO2023083228A1 publication Critical patent/WO2023083228A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/08—Reselecting an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/20—Manipulation of established connections
    • H04W76/25—Maintenance of established connections

Definitions

  • the embodiments of the present application relate to the field of communication transmission, and in particular, to a base station handover method, a base station, and a computer-readable storage medium.
  • the core network control plane and user plane are often separated, and the control plane can be shared with the public network.
  • the user plane is basically deployed locally in the industry park and separated from the public network.
  • the base station and the user plane network element of the core network used in the industry are deployed locally, the physical distance is relatively close, and the transmission is stable; but the distance between the base station and the public network is long, the transmission link is complicated, and any one of the fiber failure, optical port module abnormality, and backhaul link Node failures will cause users to be released abnormally, and the business of industrial applications will be forced to be interrupted.
  • this kind of abnormality may be that they miss a call, cannot continue to watch movies, and cannot download web pages.
  • network status connections such as smart mines, drones, smart hospitals, smart manufacturing factory workshops, etc.
  • the network connection status is related to the safe production of the unit, especially when the terminal movement will affect the business connection status.
  • a broken link with the core network may cause economic losses to industry units and may also lead to security incidents.
  • the main purpose of the embodiments of the present application is to provide a base station handover method, a base station, and a computer-readable storage medium, so that the base station will not be disconnected from the core network during the handover process of the base station.
  • the embodiment of the present application provides a base station handover method, which is applied to the second base station, including:
  • the handover request carrying the identity of the user equipment UE and the identity of the first base station; establishing a connection with the UE according to the identity of the UE; when there is a connection with the core network In an abnormal situation, the UE is not released, and the downlink message of the UE from the core network forwarded by the first base station is received.
  • the embodiment of the present application further provides a base station, including: a response module, configured to respond to the handover request of the first base station, where the handover request carries the identity of the user equipment UE and the identity of the first base station identification; a connection module, configured to establish a connection with the UE according to the identity of the UE; a processing module, configured to receive the UE forwarded by the first base station without releasing the UE when there is an abnormal connection with the core network The downlink message of the UE from the core network.
  • a response module configured to respond to the handover request of the first base station, where the handover request carries the identity of the user equipment UE and the identity of the first base station identification
  • a connection module configured to establish a connection with the UE according to the identity of the UE
  • a processing module configured to receive the UE forwarded by the first base station without releasing the UE when there is an abnormal connection with the core network The downlink message of the UE from the core network.
  • an embodiment of the present application further provides a base station, including: at least one processor; and a memory connected to the at least one processor in communication; wherein, the memory stores information that can be used by the at least one processor.
  • a base station including: at least one processor; and a memory connected to the at least one processor in communication; wherein, the memory stores information that can be used by the at least one processor.
  • An instruction executed by a processor the instruction is executed by the at least one processor, so that the at least one processor can execute the above scheduling method.
  • an embodiment of the present application further provides a computer-readable storage medium storing a computer program, and implementing the above scheduling method when the computer program is executed by a processor.
  • the UE after receiving the handover request from the first base station, if the connection between the second base station and the core network is abnormal, the UE is not released, and the source base station with the initial link abnormality can continue to forward the downlink message For the next base station, such as forwarding to the second base station through the first base station, that is, even if the second base station to which the UE switches is abnormally connected to the core network, it can still obtain the downlink message of the core network, so that the UE can obtain the downlink message of the core network during the switching process of the base station. , will not break the link with the core network, and ensure the service connection of the UE during the mobile process.
  • FIG. 1 is a schematic flowchart of a base station handover method provided according to an embodiment of the present application
  • Fig. 2 is a schematic diagram of an application scenario provided according to an embodiment of the present application.
  • Fig. 3 is a schematic diagram 1 of a base station handover method provided according to an embodiment of the present application.
  • FIG. 4 is a second schematic diagram of a base station handover method provided according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram 3 of a base station handover method provided according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram 4 of a base station handover method provided according to an embodiment of the present application.
  • FIG. 7 is a schematic diagram of modules of a base station according to an embodiment of the present application.
  • Fig. 8 is a schematic structural diagram of a base station according to an embodiment of the present application.
  • first and second in the embodiments of the present application are used for description purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Thus, the features defined as “first” and “second” may explicitly or implicitly include at least one of these features.
  • the terms “including” and “having” and any variations thereof are intended to cover non-exclusive inclusion. For example, a system, product or equipment comprising a series of components or units is not limited to the listed components or units, but optionally also includes components or units not listed, or optionally also includes the components or units for these products or Other parts or units inherent in equipment.
  • “plurality” means at least two, such as two, three, etc., unless otherwise specifically defined.
  • the control plane link between the target base station and the core network is abnormal, such as N4 link disconnection, which causes the control plane network element (Access and Mobility Management Function, AMF) of the core network and the core network
  • AMF Access and Mobility Management Function
  • UPF User Plane Function
  • the method provided in the embodiment of the present application ensures smooth handover of the terminal and uninterrupted services by performing a series of processing on the base station and core network AMF, session management function (SMF) and UPF.
  • SMF session management function
  • An embodiment of the present application relates to a base station switching method, which is applied to a second base station.
  • the specific process is shown in FIG. 1 .
  • the implementation details of the base station handover method in this embodiment are described below in detail.
  • the following content is only implementation details provided for easy understanding, and is not necessary for implementing this solution.
  • the application scenarios of the embodiments of the present application may include but are not limited to: the base station and the core network user plane network elements are deployed in the campus, the core network control plane network elements are deployed in the operator's central computer room, and the base station is transmitted remotely through a router.
  • Switches, etc. as shown in Figure 2, where Xn is the interface for information transmission between base stations, N2 is the interface for information transmission between the base station and the core network control plane network elements, and N3 is the interface between the base station and the core network user plane network elements N4 is the interface between network elements of the core network, N6 is the interface from the core network to external enterprises/Internet, and gNB refers to the base station.
  • the base station and core network elements such as the N2 link between the 5G base station gNB and the core network control plane network element AMF, and the N4 link between the core network SMF and the core network UPF
  • the base station and core network elements such as AMF, SMF, and UPF keep the terminal in the vertical industry connection state, that is, the ToB RRC-Connected UE online and do not release it.
  • the following terminals or user equipment (User Equipment, UE) all refer to vertical industry connection state terminals.
  • the slice information carried by the access can be identified.
  • Step 101 responding to the handover request of the first base station, the handover request carrying the identity of the user equipment UE and the identity of the first base station;
  • Step 102 establishing a connection with the UE according to the identity of the UE;
  • Step 103 When the connection with the core network is abnormal, the UE is not released, and the downlink message of the UE from the core network forwarded by the first base station is received.
  • the UE after receiving the handover request from the first base station, if the connection between the second base station and the core network is abnormal, the UE is not released, and the source base station with the initial link abnormality can continue to forward the downlink message to the next
  • the base station for example, is forwarded to the second base station through the first base station, that is, the second base station to which the UE is switched can obtain the downlink message of the core network even if the connection with the core network is abnormal, so that the UE will not A disconnected state occurs with the core network to ensure service connection during UE mobility.
  • a handover request of a first base station is responded to, and the handover request carries an identity of a user equipment UE and an identity of the first base station. That is, the second base station, as the target base station, receives the handover request from the first base station as the source base station, and simultaneously receives the identity of the first base station and the identity of the UE, for the second base station to establish a connection.
  • the UE initiates a measurement report (Measure Report, MR) to trigger cross-site handover from the first base station to the second base station.
  • the initiation of the measurement report may be due to the location movement of the terminal.
  • the first base station sends the handover request signaling Handover Request to the second base station, which carries the sending address of the UE uplink message (UL NG-U UP TNL Information at UPF), that is, the second base station has received the uplink user plane path information .
  • the identity of the first base station is the source cell global identifier (gNB1Source Cell Global ID, gNB1NCGI) of the first base station.
  • the handover request carrying the identity of the UE includes: the handover request carrying the identity assigned to the UE by the first base station; the responding to the handover request of the first base station includes: saving the identity of the first base station and the identity assigned to the UE by the first base station; sending the identity of the second base station and the identity assigned to the UE by the second base station to the the first base station. That is, the second base station accepts the UE according to its own admission congestion processing algorithm when resources permit, and the second base station will feed back a Handover Request Acknowledge after agreeing to the UE's access, which is used to reply to the handover request signaling, indicating that access is allowed. It carries the random access resource when the UE accesses the target cell.
  • the second base station saves the source UE XnAP ID (Source NG-RAN node UE XnAP ID reference) of the UE assigned by the first base station, and the first base station saves the target UE XnAP ID (Target NG-RAN node ) of the UE assigned by the second base station UE XnAP ID) and the source UE XnAP ID (Source NG-RAN node UE XnAP ID) generated by itself.
  • the source UE XnAP ID Source NG-RAN node UE XnAP ID reference
  • a connection is established with the UE according to the identity of the UE; the first base station notifies the UE to switch to the second base station (target base station) through an RRC reconfiguration command (RRCReconfiguration), after which there is no data on the uplink and downlink air interfaces, and the second A base station starts to forward the downlink message to the second base station, and the UE accesses the second base station.
  • the UE and the second base station perform uplink and downlink air interface data transmission; the second base station receives and analyzes the sending address of the UE uplink message, and The UE performs packet transmission.
  • the source base station usually has a timer (TXnRELOCoverall), which is used to monitor when the source base station does not receive an instruction to release the context sent by the target base station within a predetermined time after forwarding the downlink message. It will instruct the source base station to release the UE context by itself.
  • TXnRELOCoverall a timer used to monitor when the source base station does not receive an instruction to release the context sent by the target base station within a predetermined time after forwarding the downlink message. It will instruct the source base station to release the UE context by itself.
  • the context needs to be kept for a long time, so if a connection abnormality occurs during the handover of the base station, the timer is triggered to be closed.
  • step 103 if the connection with the core network is abnormal, the UE is not released, and the downlink message of the UE from the core network forwarded by the first base station is received. That is, when the UE is handed over from the first base station to the second base station, or later to the third base station, if the conventional handover process defined by the 3GPP protocol has not been completed, the downlink message will be forwarded through the original source station.
  • the source station is the first base station that has not completed the normal handover process. Wherein, whenever the terminal is handed over to a cell, as long as the handover execution phase is not completed normally, it will be marked as an abnormal handover terminal.
  • the connection abnormality includes: abnormal connection with the control plane network element of the core network or receiving a path change failure message sent by the core network. For example, when the UE moves to the edge of the cell and the MR report is triggered, if the link between the target base station and the core network in the handover process is normal, after the UE accesses the target cell, the path initiated by the target base station in the target cell to the core network The change request may fail due to the disconnection of core network elements (for example, abnormal N4 link connection). Although the target base station cannot monitor the connection status between core network elements, it will receive a route change failure message sent by the core network.
  • core network elements for example, abnormal N4 link connection
  • the target base station If the connection between the target base station and the control plane network element of the core network is abnormal, for example, the N2 link connection is abnormal, after the UE accesses the target cell, the target base station does not initiate a path change request process. That is, the target base station will not release the user due to the above two connection abnormalities.
  • the UE when the connection is abnormal, the UE is not released, and the downlink user plane path is to rely on the source base station (first base station) to forward the downlink message to the target base station (second base station), that is, the second base station is Obtain the downlink message sent by the core network through the first base station; and the first base station maintains the terminal context until the second base station notifies the release of the context information of the UE, that is, the first base station receives the UE Context Release signaling sent by the second base station , release it.
  • the target base station continuously receives the downlink packets forwarded by the source station and sends them to the UE through the air interface.
  • the uplink user plane path has been sent by the source base station to the target base station in step 101, and the address of the core network user plane network element (such as UPF) for industrial applications is unique, so the uplink user plane path is not affected by link disconnection.
  • the second base station initiates a Path Switch Request (Path Switch Request) to the AMF as the target base station;
  • the session is not released, but the path change request cannot be delivered to the UPF, and the second base station is notified of the path change failure (Path Switch Request Failure).
  • the second base station does not release the UE, and maintains the UE session and context.
  • the downlink message is continuously forwarded from the first base station to the second base station according to the original path, and then sent to the UE over the air interface. As long as the first base station does not receive the End message from the UPF The Marker command will continue to forward the downlink message, and maintain the context of the cut-out UE and the source UE XnAP ID (Source NG-RAN node UE XnAP ID reference) assigned by the first base station of this handover and the target UE XnAP assigned by the second base station ID (Target NG-RAN node UE XnAP ID).
  • source UE XnAP ID Source NG-RAN node UE XnAP ID reference
  • the receiving the downlink message of the UE from the core network forwarded by the first base station includes: sending a handover request to a third base station, where the handover request sent to the third base station carries The identity identifier assigned to the UE by the second base station and the identity identifier of the second base station; after the UE is handed over to the third base station, the downlink message forwarded by the first base station forwarded to the third base station.
  • the second base station represents the transit base station
  • the third base station represents the latest target base station
  • the handover execution stage cannot Normal operation (N2 or N4 may be disconnected)
  • the downlink maintains the user plane path when the link is disconnected, that is, the forwarding process of the downlink message is continued.
  • the link disconnected The handover source base station (the second base station) forwards the downlink message to the latest target base station (the third base station), as shown in FIG.
  • the transit base station such as gNB2 in Figure 3, maintains the context of the UE, as well as the source UE XnAP ID and gNB1NCGI of gNB1 when the UE switches in, and the target UE XnAP ID allocated by the cell where gNB2 is located as the target cell, and the one allocated by gNB3 when switching out Target UE XnAP ID and gNB3 Source Cell Global ID (gNB3Source Cell Global ID, gNB3NCGI).
  • gNB3Source Cell Global ID, gNB3NCGI gNB3Source Cell Global ID, gNB3NCGI
  • gNB3 is the latest target base station, and the AMF between gNB3 and the core network is disconnected: UE initiates MR; gNB2 initiates a handover request to gNB3; N2 between gNB3 and AMF is disconnected , gNB3, AMF, UPF, and SMF keep the UE session and do not release it.
  • gNB3 normally accepts the UE and replies with Handover Request Acknowledge, which means access is allowed.
  • gNB2 saves the source UE XnAP ID reference (assigned by gNB2) and target UE XnAP ID (assigned by gNB3) of the switched-out UE, and gNB3 also saves the XnAP ID mapping relationship; gNB2 sends an RRC reset command to notify UE to perform the handover, and then gNB2 goes up and down There is no data on the uplink air interface, and the downlink data is forwarded from UPF to gNB1 via gNB1, and then forwarded to gNB3. The UE accesses the target base station gNB3. At this time, the UE and gNB3 perform uplink and downlink air interface data transmission.
  • gNB3 cannot initiate the path change process.
  • the downlink message is continuously forwarded from gNB1 to gNB2 according to the original path, then forwarded from gNB2 to gNB3, and then sent to the UE over the air interface.
  • the gNB that forwards the message does not receive the End Marker command, it will continue to forward the downlink message and maintain the context of the UE.
  • the process of cross-site switching downlink message forwarding remains unchanged.
  • gNB1 is switched to gNB2
  • gNB2 is switched to gNB3, N4 between AMF and UPF is abnormal, and AMF between gNB3 and the core network is disconnected, refer to Figure 4 for the data transmission process.
  • each base station on the downlink forwarding path must maintain the UE XnAP ID and NCGI mapping table before and after the UE handover.
  • the mapping table includes UE XnAP IDs allocated by each base station on the forwarding path of the downlink message, respectively allocated by the upstream and downstream base stations, and the global cell identifiers of the upstream and downstream base stations.
  • after handing over the UE to the third base station it further includes: responding to a handover request sent by the fourth base station, the handover request of the fourth base station carrying the identity assigned to the UE by the fourth base station identification and the identity of the fourth base station; after determining that the fourth base station is the third base station according to the identity of the fourth base station and the identity allocated to the UE by the fourth base station, the In the case that the above UE is the same, stop forwarding the downlink message to the third base station; notify the third base station to release the context of the UE.
  • the third base station is used as the source base station for this switchback, and the source UE XnAP ID assigned by the third base station will be equal to the UE's last handover to the third base station.
  • the third base station is used as the target UE XnAP ID assigned to it by the target base station.
  • the second base station receives a handover request from other base stations, it will be treated as the fourth base station.
  • the target UE XnAP ID and NCGI in the second handover process are also the same, and it is recognized that the fourth base station is the third base station and the UE is also the same UE.
  • the base station was handed over last time, and the third base station was the last target base station, that is, the second base station was forwarding downlink messages to the third base station after the last base station handover, and during this handover process , it is recognized that the latest state is that the second base station is the target base station of the third base station, so the original behavior of the second base station to forward the downlink message to the third base station is stopped, and the redundant transfer path of the downlink message is reduced.
  • gNB1 represents the first base station
  • gNB2 represents the second base station
  • gNB3 represents the third base station.
  • the downlink packets are forwarded to gNB3 through gNB1 step by step. After the UE accesses gNB3, Then send it to the UE over the air interface. At this time, if the UE switches back to gNB2, then: UE initiates MR to trigger cross-site handover; gNB3 initiates a handover request to gNB2, and gNB3 learns that the UE is switched out from gNB2 through the UE XnAP ID of the UE switching path and the NCGI of the corresponding cell Cut in again.
  • gNB3 uses the target UE XnAP ID 6 as the source UE XnAP ID when the UE switched in last time to send a handover request to gNB2.
  • gNB2 After gNB2 receives the handover request signaling, it analyzes that the source UE XnAP ID carried in it is the target UE XnAP ID 6 allocated by the target base station during the last handover, and the cell NCGI that sent the handover request is also the target of the last handover At the same time, the UE context is always there. At this time, gNB2 stops the downlink forwarding of the UE message and changes it to local storage.
  • the gNB2 After judging that the switched-in UE is the UE being forwarded by the gNB2 station, the gNB2 replies the handover request signaling to the gNB3.
  • the air interface of gNB3 sends an RRC reset command to notify the UE to switch to gNB2, after which there is no data on the uplink and downlink air interfaces.
  • the UE accesses gNB2, and the UE and gNB2 perform uplink and downlink air interface data transmission.
  • it may also include: gNB2 notifies gNB3 to release all information about the UE, such as the UE Context.
  • gNB3 reclaims the previously allocated UE XnAP ID, and deletes the previously maintained UE XnAP ID and NCGI mapping table.
  • the UE when the UE repeatedly switches between two abnormal sites, for example, as shown in Figure 3, the UE switches back to gNB2 after switching from gNB2 to gNB3. For example, because the strongest cell in the MR sent by the UE to gNB3 is gNB2, gNB3 Later, it was found that the NCGI of gNB2 was the source base station accessed last time.
  • the source UE XnAP ID carried in the handover request message initiated by gNB3 at this time is the target UE XnAP ID allocated during the last access, so that gNB2 compares the NCGI of the handover request gNB3 with the NCGI of the target base station when the abnormal handover terminal was switched out last time Same, compare the UE XnAP ID carried in this handover request with the same UE XnAP ID assigned by the target base station gNB3 when the abnormal handover terminal was switched out last time, that is, the same NCGI, and the same UE XnAP ID, it can be identified that the UE is the previous abnormal Switch terminals.
  • the downlink packet forwarding is ended, and the packet is directly transmitted to the terminal through the air interface, and the source station gNB3 of this handover is notified to release the UE context.
  • the specific data sending and receiving process may refer to FIG. 5 .
  • the method includes: sending an instruction to release the UE to the first base station when disconnection is required. For example, if the UE is doing business at the second base station after the abnormal handover, if the UE needs to be released, the second base station will notify the first base station to release the UE and clear the local information such as the UE context; if the UE is doing business at the third base station after the handover service, the UE needs to be released, the third base station first notifies the second base station to release the UE according to the switching in and out mapping table, the second base station transmits the signaling to the first base station, and then locally clears the UE context and other information, the first base station This operation is also performed until the first base station with an abnormal handover receives a release command.
  • the upper-level base stations on the downlink packet forwarding path need to send the instruction to release the UE until the first source base station receives the release instruction. It may be caused only by the target base station.
  • the first source base station does not limit whether its state is abnormal or not.
  • the situation that disconnection is required includes: the second base station detects that the radio link with the UE fails; or receives a reestablishment request sent by the UE to the second base station.
  • the second base station here represents the base station that is connecting with the UE and doing business, that is, the last target base station in the handover process.
  • the need to disconnect may be detected autonomously by the target base station being connected to the UE, for example, due to radio link failure or other reasons; or the UE needs to disconnect due to other reasons, and will actively initiate the RRC reestablishment process.
  • the target base station receives the RRC reestablishment process, it first initiates the UE release process (UE Context Release) to the upper base station.
  • the transit base station After receiving the UE Context Release message, the transit base station forwards it to the upper-level base station on the downlink message forwarding path, and then releases the UE Context Release message. Information such as the context of the UE, until the UE Context Release message is delivered to the source base station that initially failed the handover.
  • after receiving the downlink message of the UE from the core network forwarded by the first base station includes: sending a handover request to a third base station; after receiving the core network feedback from the core network and When the third base station is connected to a normal instruction, stop forwarding the downlink message to the third base station; wherein, the instruction fed back by the core network is obtained through the first base station. That is, when the connection between the third base station and the core network is normal, the first base station will receive an instruction from the core network that the connection is normal, and there is no need to forward the downlink message to the third base station along the downlink message forwarding path.
  • the message forwarding path can be embodied by the aforementioned mapping table; on the downlink message forwarding path, the second base station as the superior of the third base station will receive the instruction that the connection is normal forwarded by the first base station step by step, that is, no longer send The third base station forwards the downlink message; the third base station directly interacts with the core network and the UE for context data, without maintaining the downlink message forwarding process established in the previous handover process. Wherein, multiple transit base stations are allowed to exist between the first base station and the second base station.
  • the second base station which is the upper level of the third base station in the downlink message forwarding path, will receive the UE Context Release sent by the third base station, thereby releasing The context information of the UE, and forwarding the release instruction to the first base station step by step, for the first base station to perform UE release.
  • the base station that is normally connected to the core network is gNB4 (N2, N4 links are available), that is, gNB4 refers to the connection between the above-mentioned core network and the core network.
  • the normal third base station, gNB3 refers to the second base station above the normal third base station connected to the core network
  • gNB1 refers to the first base station with abnormal switching, that is, the first base station
  • gNB2 refers to the first base station Between the second base station, although not mentioned, other transit base stations are allowed to exist.
  • the last target base station is gNB4.
  • UE initiates MR and triggers cross-site handover;
  • gNB3 initiates a handover request to gNB4;
  • gNB4 accepts the UE if resources permit according to its own admission congestion processing algorithm, and replies to allow handover request signaling;
  • gNB3 sends an RRC reset command to inform UE to execute After switching, there is no data on the uplink and downlink air interfaces;
  • UE accesses gNB4, and at this time UE and gNB4 perform data transmission on uplink and downlink air interfaces;
  • gNB4 initiates a Path Switch Request to AMF as the target base station;
  • AMF, SMF and UPF interact with the path change process, and
  • UPF sends
  • the End Marker notifies gNB1 of the end of downlink data forwarding, gNB1 forwards the End Marker to gNB2 according to the previously maintained UE XnAP ID and the NCGI of the target
  • gNB4 When gNB4 receives AMF's normal connection feedback (PATH SWITCH REQUEST ACKNOWLEDGE) through N2; gNB4 sends UE Context Release to notify gNB3 to release the UE context information. gNB3 forwards this signaling to gNB2, and at the same time releases the UE context-related air interface and control plane locally. If there is downlink data forwarding, it will continue. Maintained UE XnAP ID and NCGI mapping table. gNB2 forwards the UE Context Release signaling to gNB1, and at the same time locally releases the air interface and control plane part related to UE Context. If there is downlink data forwarding, it will continue.
  • mapping table If the forwarding is completed, all the UE information will be cleared, and the previously allocated UE XnAP ID will be recovered. Delete the previously maintained UE XnAP ID and NCGI mapping table. gNB1 locally releases the air interface and control plane related to the UE Context. If there is downlink data forwarding, it will continue. If the forwarding is completed, all the UE information will be cleared, the previously allocated UE XnAP ID will be recovered, and the previously maintained UE XnAP ID and NCGI will be deleted. mapping table.
  • the Path Switch Request process initiated by the base station is successful.
  • the core network user plane network element (such as UPF) will change the downlink path to the current base station (gNB4), and send an End Marker to notify the original source base station, and stop the forwarding process of downlink packets step by step.
  • the target base station as shown in Figure 3, gNB4 initiates UE Context Release to the superior base station gNB3, and gNB3, as a transit base station, transfers the UE Context Release to the superior base station gNB2, and then clears the local context of the UE.
  • gNB2 serves as a transit base station and delivers UE Context Release to the upper-level base station gNB1, it clears the local context of the UE. After receiving the UE Context Release as the initial source base station, gNB1 releases all information of the UE if the End Marker is sent out. Refer to Figure 6 for the specific data transmission process.
  • the UE after receiving the handover request from the first base station, if the connection between the second base station and the core network is abnormal, the UE is not released, and the source base station with the initial link abnormality can continue to forward the downlink message to the The next base station, for example, forwards to the second base station through the first base station, that is, even if the second base station to which the UE switches is abnormally connected to the core network, it can still obtain the downlink message of the core network, so that the UE is in the process of switching base stations. There will be no link disconnection with the core network, ensuring service connection during UE mobility.
  • the previously established downlink packet forwarding path stops forwarding downlink packets, and all the base stations on the path release the UE. Only the information transmission path between the target base station, core network, and UE is reserved; that is, after switching to a normal base station, the release of the previous path is triggered to reduce resource occupation. In addition, when two base stations with abnormal connections are switched back and forth, repeated switching is identified to reduce the redundant transfer path of downlink messages.
  • step division of the above various methods is only for the sake of clarity of description. During implementation, it can be combined into one step or some steps can be split and decomposed into multiple steps. As long as they include the same logical relationship, they are all within the scope of protection of this patent. ; Adding insignificant modifications or introducing insignificant designs to the algorithm or process, but not changing the core design of the algorithm and process are all within the scope of protection of this patent.
  • An embodiment of the present application relates to a base station, as shown in FIG. 7 , including:
  • the response module 201 is configured to respond to the handover request of the first base station, where the handover request carries the identity of the user equipment UE and the identity of the first base station;
  • a connection module 202 configured to establish a connection with the UE according to the identity of the UE;
  • the processing module 203 is configured to receive the downlink message of the UE forwarded by the first base station from the core network without releasing the UE when the connection with the core network is abnormal.
  • the handover request carries the identity of the user equipment UE, for example: the handover request carries the identity assigned to the UE by the first base station; the response to the handover request of the first base station, For example: saving the identity of the first base station and the identity assigned to the UE by the first base station; sending the identity of the second base station and the identity assigned to the UE by the second base station to the first base station.
  • the connection is abnormal, for example: the connection with the control plane network element of the core network is abnormal; or the path change failure message sent by the core network is received.
  • the first base station after receiving the downlink message from the UE of the core network forwarded by the first base station, it includes: responding to a handover request sent by a third base station, the handover request of the third base station carrying the The identity mark assigned to the UE by the third base station and the identity mark of the third base station; when the third base station is determined to be abnormally handed over last time according to the identity mark of the third base station, responding to the handover of the second base station requesting base station, and the identity assigned to the UE by the third base station is the identity assigned to the UE by the base station that responded to the handover request of the second base station during the last abnormal handover, stop sending to the third base station
  • the three base stations forward the downlink message issued by the core network; and notify the third base station to release the context of the UE.
  • the receiving the downlink message of the UE from the core network forwarded by the first base station includes: sending an instruction to release the UE to the first base station when the connection needs to be disconnected .
  • the situation that the connection needs to be disconnected includes: the second base station detects that the wireless link with the UE fails; or receives a reestablishment request sent by the UE to the second base station.
  • the first base station after receiving the downlink message of the UE from the core network forwarded by the first base station, it includes: sending a handover request to a third base station; In the case of an instruction indicating that the connection between the network and the third base station is normal, stop forwarding the downlink message to the third base station; wherein, the instruction fed back by the core network is obtained through the first base station.
  • the UE after receiving the handover request from the first base station, if the connection between the second base station and the core network is abnormal, the UE is not released, and the source base station with the initial link abnormality can continue to forward the downlink message to the next
  • the base station for example, is forwarded to the second base station through the first base station, that is, the second base station to which the UE is switched can obtain the downlink message of the core network even if the connection with the core network is abnormal, so that the UE will not A disconnected state occurs with the core network to ensure service connection during UE mobility.
  • this embodiment is a system embodiment corresponding to the above embodiment, and this embodiment can be implemented in cooperation with the above embodiment.
  • the relevant technical details mentioned in the foregoing implementation manners are still valid in this implementation manner, and will not be repeated here in order to reduce repetition.
  • the relevant technical details mentioned in this implementation manner may also be applied in the foregoing implementation manners.
  • modules involved in this embodiment are logical modules.
  • a logical unit can be a physical unit, or a part of a physical unit, or multiple physical units. Combination of units.
  • units that are not closely related to solving the technical problems proposed in the present application are not introduced in this embodiment, but this does not mean that there are no other units in this embodiment.
  • One embodiment of the present application relates to a base station, as shown in FIG. 8 , including at least one processor 301; and a memory 302 communicatively connected to the at least one processor 301; Instructions executed by the at least one processor 301, the instructions are executed by the at least one processor, so that the at least one processor can execute the above base station handover method.
  • the memory and the processor are connected by a bus
  • the bus may include any number of interconnected buses and bridges, and the bus connects one or more processors and various circuits of the memory together.
  • the bus may also connect together various other circuits such as peripherals, voltage regulators, and power management circuits, all of which are well known in the art and therefore will not be further described herein.
  • the bus interface provides an interface between the bus and the transceivers.
  • a transceiver may be a single element or multiple elements, such as multiple receivers and transmitters, providing means for communicating with various other devices over a transmission medium.
  • the data processed by the processor is transmitted on the wireless medium through the antenna, and further, the antenna receives the data and transmits the data to the processor.
  • the processor is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interface, voltage regulation, power management, and other control functions. Instead, memory can be used to store data that the processor uses when performing operations.
  • One embodiment of the present application relates to a computer-readable storage medium storing a computer program.
  • the above method embodiments are implemented when the computer program is executed by the processor.
  • the aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-OnlyMemory), random access memory (RAM, RandomAccessMemory), magnetic disk or optical disk and other media that can store program codes.

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Abstract

本申请实施例涉及通信传输领域，特别涉及一种基站切换方法、基站和计算机可读存储介质。上述基站切换方法包括：响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；根据所述UE的身份标识与所述UE建立连接；在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。

Description

基站切换方法、基站和计算机可读存储介质
相关申请
本申请要求于2021年11月10日申请的、申请号为202111327079.5的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及通信传输领域，特别涉及一种基站切换方法、基站和计算机可读存储介质。
背景技术
传统的网络连接状态中只要接入网与核心网之间断链，立即释放所有在网用户。对于垂直行业应用的移动通信网络，核心网控制面和用户面往往是分开的，且控制面可以和公网共用，用户面基本是行业园区本地部署，与公网分离。基站与行业应用的核心网用户面网元本地部署，物理距离较近，传输稳定；但基站与公网距离较远，传输链路复杂，光纤故障、光口模块异常、后传链路任何一个结点故障都会引发用户被异常释放，行业应用的业务会被迫中断。
这种异常对于普通的公网用户可能是错过一个电话，无法继续看电影，网页无法下载。但对网络状态连接有较高要求的垂直行业，比如智慧矿井，无人机，智慧医院，智能制造工厂车间等，网络连接情况事关单位安全生产，尤其当终端移动会影响业务连接情况，一旦与核心网之间断链，对行业单位可能造成经济损失，还可能引发安全事故。
发明内容
本申请实施例的主要目的在于提出一种基站切换方法、基站和计算机可读存储介质，使得在基站的切换过程中，不会与核心网断联。
为实现上述目的，本申请实施例提供了一种基站切换方法，应用于第二基站，包括：
响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；根据所述UE的身份标识与所述UE建立连接；在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。
为实现上述目的，本申请实施例还提供一种基站，包括：响应模块，用于响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；连接模块，用于根据所述UE的身份标识与所述UE建立连接；处理模块，用于在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。
为实现上述目的，本申请实施例还提供了一种基站，包括：至少一个处理器；以及，与所述至少一个处理器通信连接的存储器；其中，所述存储器存储有可被所述至少一个处理器执行的指令，所述指令被所述至少一个处理器执行，以使所述至少一个处理器能够执行上述的调度方法。
为实现上述目的，本申请实施例还提供了一种计算机可读存储介质，存储有计算机程序，所述计算机程序被处理器执行时实现上述的调度方法。
本申请提出的基站切换方法，在接收第一基站的切换请求后，若第二基站与核心网之间的连接异常，保持UE不释放，最初链路异常的源基站可持续将下行报文转发给下一个基站，比如通过第一基站转发到第二基站，也就是UE切换到的第二基站即使与核心网连接异常，也能够获取核心网的下行报文，使得UE在切换基站的过程中，不会与核心网产生断链的状态，保证UE移动过程中的的业务连接。
附图说明
图1是根据本申请一个实施例所提供的基站切换方法的流程示意图；
图2是根据本申请一个实施例所提供的应用场景的示意图；
图3是根据本申请一个实施例所提供的一种基站切换方法的示意图一；
图4是根据本申请一个实施例所提供的一种基站切换方法的示意图二；
图5是根据本申请一个实施例所提供的一种基站切换方法的示意图三；
图6是根据本申请一个实施例所提供的一种基站切换方法的示意图四；
图7是根据本申请一个实施例的基站的模块示意图；
图8是根据本申请一个实施例的基站的结构示意图。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合附图对本申请的各实施例进行详细的阐述。然而，本领域的普通技术人员可以理解，在本申请各实施例中，为了使读者更好地理解本申请而提出了许多技术细节。但是，即使没有这些技术细节和基于以下各实施例的种种变化和修改，也可以实现本申请所要求保护的技术方案。以下各个实施例的划分是为了描述方便，不应对本申请的具体实现方式构成任何限定，各个实施例在不矛盾的前提下可以相互结合相互引用。
本申请实施例中的术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。本申请的描述中，术语“包括”和“具有”以及它们任何变形，意图在于覆盖不排他的包含。例如包含了一系列部件或单元的系统、产品或设备没有限定于已列出的部件或单元，而是可选地还包括没有列出的部件或单元，或可选地还包括对于这些产品或设备固有的其它部件或单元。本申请的描述中，“多个”的含义是至少两个，例如两个，三个等，除非另有明确具体的限定。
当垂直行业的终端即ToB UE跨站切换时，目标基站与核心网之间控制面链路异常，比如N4断链，导致核心网控制面网元(Access and Mobility Management Function，AMF)和核心网用户面网元(User Plane Function，UPF)之间无法信息交互的情况；比如N2断链，出现基站和AMF之间无法信息交互的情况。本申请实施例中提供的方法，通过对基站与核心网AMF、会话管理网元(Session Management Function，SMF)和UPF进行一系列处理，保障终端顺利切换，业务不中断。
本申请的一个实施例涉及一种基站切换方法，应用于第二基站。具体流程如图1所示， 下面对本实施例的基站切换方法的实现细节进行具体的说明，以下内容仅为方便理解提供的实现细节，并非实施本方案的必须。
本申请的实施例的应用场景可以包括但不限于：基站与核心网用户面网元部署在园区内，核心网控制面网元部署在运营商中心机房，与基站远距离传输，中间经过路由器，交换机等，如图2所示，其中Xn为基站间进行信息传输的接口，N2为基站与核心网控制面网元之间进行信息传输的接口，N3为基站到核心网用户面网元之间的接口，N4为核心网网元间接口，N6为核心网到外部企业/互联网的接口，gNB指代基站。在基站和核心网之间的控制面或者核心网网元之间(比如5G基站gNB与核心网控制面网元AMF间的N2链路，核心网SMF与核心网UPF间的N4链路)传输异常时，基站、核心网各网元如AMF、SMF和UPF保持垂直行业连接态终端即ToB RRC-Connected UE在线不释放。以下终端或用户设备(User Equipment，UE)都指的是垂直行业连接态终端。通过接入携带的切片信息可识别。
步骤101，响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；
步骤102，根据所述UE的身份标识与所述UE建立连接；
步骤103，在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。
本实施例中，在接收第一基站的切换请求后，若第二基站与核心网之间的连接异常，保持UE不释放，最初链路异常的源基站可持续将下行报文转发给下一个基站，比如通过第一基站转发到第二基站，也就是UE切换到的第二基站即使与核心网连接异常，也能够获取核心网的下行报文，使得UE在切换基站的过程中，不会与核心网产生断链的状态，保证UE移动过程中的的业务连接。
下面对本实施方式的基站切换方法的实现细节进行具体的说明，以下内容仅为方便理解提供的实现细节，并非实施本方案的必须。
在步骤101中，响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识。即第二基站作为目标基站，接收第一基站作为源基站的切换请求，同时接收第一基站中的身份标识和UE的身份标识，供第二基站建立连接。
在一个例子中，UE发起测量报告(Measure Report，MR)，触发跨站切换，从第一基站切换到第二基站，该测量报告的发起可能是由于终端的位置移动等。第一基站向第二基站发送切换请求信令Handover Request，里面携带了该UE上行报文的发送地址(UL NG-U UP TNL Information at UPF)，也就是第二基站收到了上行用户面路径信息。其中，第一基站的身份标识为第一基站的源小区全球标识(gNB1Source Cell Global ID，gNB1NCGI)。
在一些例子中，所述切换请求中携带UE的身份标识，包括：所述切换请求中携带所述第一基站分配给所述UE的身份标识；所述响应第一基站的切换请求，包括：保存所述第一基站的身份标识和所述第一基站分配给所述UE的身份标识；将所述第二基站的身份标识和所述第二基站分配给所述UE的身份标识发送至所述第一基站。即，第二基站根据自身接纳拥塞处理算法，在资源允许的情况下接纳该UE，第二基站同意该UE接入后会反馈Handover Request Acknowledge，用于回复切换请求信令，表示允许接入，里面携带UE接入目标小区时的随机接入资源。第二基站保存第一基站分配的该UE的源UE XnAP ID(Source NG-RAN node UE XnAP ID reference)，第一基站保存第二基站分配的该UE的目标UE XnAP ID(Target  NG-RAN node UE XnAP ID)和自身生成的源UE XnAP ID(Source NG-RAN node UE XnAP ID)。
在步骤102中，根据所述UE的身份标识与所述UE建立连接；第一基站通过RRC重置指令(RRCReconfiguration)通知UE切换到第二基站(目标基站)，此后上下行空口无数据，第一基站开始转发下行报文给第二基站，UE接入到第二基站，此时UE和第二基站进行上下行空口数据传输；第二基站接收并解析上述UE上行报文的发送地址，与UE进行报文传输。
另外，源基站通常具有定时器(TXnRELOCoverall)，用于监控源基站在对下行报文，在下行报文进行转发后，没有于预定时间内收到目标基站发送的释放上下文的指令时，定时器会自行指示源基站进行UE上下文的释放。但在本实施方式中，需要长期保持上下文，所以在若基站切换的过程中出现连接异常的情况，则触发关闭该定时器。
在步骤103中，在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。即，当UE从第一基站跨站切换到第二基站，或者在之后切到第三基站，如果没有完成3GPP协议定义的常规切换流程，下行报文就要通过最初的源站转发，最初的源站就是第一个没有完成常规切换流程的基站。其中，终端每切换到一个小区只要切换执行阶段没有正常完成，都会标记为异常切换终端。
在一些例子中，所述连接异常的情况包括：与核心网的控制面网元连接异常或收到核心网发送的路径变更失败消息。例如，当UE移动到小区边缘触发了MR上报时，如果切换过程的目标基站与核心网间的链路正常，当UE接入到目标小区后，目标小区中的目标基站向核心网发起的路径变更请求可能由于核心网网元间断链(例如N4链路连接异常)导致请求失败，虽然目标基站无法监控到核心网网元之间的连接状态，但会收到核心网发送的路径变更失败消息；如果目标基站与核心网的控制面网元连接异常，例如N2链路连接异常，当UE接入到目标小区后，目标基站不发起路径变更请求流程。也就是目标基站不会因以上两种连接异常的情况而释放用户。
在一些例子中，当出现连接异常的情况，不释放所述UE，下行用户面路径是靠源基站(第一基站)转发下行报文给目标基站(第二基站)，也就是第二基站是通过第一基站获取核心网下发的下行报文；并且第一基站保持该终端上下文，直到第二基站通知释放UE的上下文信息，即第一基站收到第二基站发送的UE Context Release信令时，进行释放。目标基站持续接收源站转发的下行报文通过空口发给UE。上行用户面路径在步骤101中源基站已经发给目标基站，且行业应用的核心网用户面网元(例如UPF)地址唯一，故上行用户面路径不受断链影响。例如，在第二基站与UE建立连接后，第二基站作为目标基站发起路径变更请求(Path Switch Request)给AMF；若核心网网元之间的N4断链，则AMF、UPF、SMF保持UE会话不释放，但路径变更请求无法送达UPF，第二基站被告知路径变更失败(Path Switch Request Failure)。此时第二基站不释放UE，维持UE会话和上下文，下行报文按原路径持续从第一基站转发到第二基站，再空口发给UE，要求第一基站只要没收到UPF发来的End Marker指令就继续转发下行报文，且维护切出UE的上下文以及本次切换的第一基站分配的源UE XnAP ID(Source NG-RAN node UE XnAP ID reference)和第二基站分配的目标UE XnAP ID(Target NG-RAN node UE XnAP ID)。
在一些例子中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：向第三基站发送切换请求，所述向第三基站发送的切换请求中携带所述第二基站分配 给所述UE的身份标识和所述第二基站的身份标识；在将所述UE切换至所述第三基站后，将所述第一基站转发的所述下行报文转发给所述第三基站。即当UE再次移动到小区边缘，触发再次跨站切换时，例如从第二基站切换到第三基站，此时第二基站代表中转基站，第三基站代表最新的目标基站；如果切换执行阶段无法正常进行(可能N2或N4断链)，此时下行维持断链时的用户面路径，也就是持续进行下行报文的转发过程，在第二基站向第三基站发送切换请求后，由断链切换的源基站(第二基站)转发下行报文到最新的目标基站(第三基站)，如图3所示，即由gNB1顺次转发至gNB3。中转基站例如图3中的gNB2，保持该UE的上下文，以及该UE切换入时的源UE XnAP ID和gNB1的gNB1NCGI，gNB2所在小区作为目标小区分配的目标UE XnAP ID，切换出时gNB3分配的目标UE XnAP ID和gNB3的源小区全球标识(gNB3Source Cell Global ID，gNB3NCGI)。以上过程中，如果gNB2的链路恢复正常，但终端已经接入gNB3，此时gNB2继续维持下行报文转发路径，不进行其他变更。
为便于理解，以一次执行过程为例。当UE从gNB2切换到gNB3，即gNB3为最新的目标基站，gNB3与核心网之间的AMF断联的情况下：UE发起MR；gNB2向gNB3发起切换请求；gNB3和AMF之间的N2断链，gNB3、AMF、UPF，SMF保持UE会话不释放。gNB3正常接纳UE，回复Handover Request Acknowledge，即允许接入。gNB2保存该切出UE的源UE XnAP ID reference(gNB2分配的)和目标UE XnAP ID(gNB3分配的)，gNB3也保存XnAP ID映射关系；gNB2发送RRC重置指令通知UE执行切换，此后gNB2上下行空口无数据，下行数据从UPF经gNB1转发给gNB2，再转发给gNB3。UE接入到目标基站gNB3，此时UE和gNB3进行上下行空口数据传输，因gNB3与AMF的N2断链，gNB3不能发起路径变更流程。下行报文按原路径持续从gNB1转发到gNB2，再从gNB2转发到gNB3，再空口发给UE。转发报文的gNB只要没收到End Marker指令，就继续转发下行报文，且维护UE的上下文。在此过程中如果gNB1与AMF的N2断链了，或者之前的N2断链又恢复了，跨站切换下行报文转发的流程都保持不变。当gNB1切换到gNB2，gNB2切换到gNB3，AMF与UPF之间的N4异常，gNB3与核心网之间的AMF断联时，数据传输过程参考图4。
对于中转基站，要维持UE的上下文、保留切入的上一级基站和切出的下一级基站信息。
另外，在UE切入到与核心网连接正常的基站之前，下行转发路径上每个基站都要维护该UE切换前后的UE XnAP ID和NCGI的映射表。该映射表中包括对于下行报文的转发路径上的每个基站保存各自分配的，和上下游基站分别分配的UE XnAP ID以及上下游基站小区全球标识。以图3中的设备为例，包括gNB1分配的源UE XnAP ID 1；gNB2分配的目标UE XnAP ID 5、gNB2分配的源UE XnAP ID 2；gNB3分配的目标UE XnAP ID 6、gNB3分配的源UE XnAP ID 3；gNB4分配的目标UE XnAP ID 7、gNB4分配的源UE XnAP ID 4。
在一些例子中，将所述UE切换至所述第三基站之后，还包括：响应第四基站发送的切换请求，所述第四基站的切换请求中携带所述第四基站分配给UE的身份标识和所述第四基站的身份标识；在根据所述第四基站的身份标识和所述第四基站分配给所述UE的身份标识，确定所述第四基站为所述第三基站，所述UE相同的情况下，停止向所述第三基站转发所述下行报文；通知所述第三基站释放所述UE的上下文。假如UE切换到第三基站后，再次切回到第二基站时，第三基站作为本次切回的源基站，第三基站分配的源UE XnAP ID就会等于UE上次切换入第三基站时第三基站作为目标基站为其分配的目标UE XnAP ID。第二基站 在接到其他基站的切换请求时，将其标为第四基站来对待，但在收到第四基站的切换请求后，能够通过切换请求中携带的信息识别源UE XnAP ID就是上次切换过程中的目标UE XnAP ID，NCGI也相同，就识别出第四基站就是第三基站且UE也是同一个UE。由于上次进行过基站切换，且第三基站为上次的目标基站，也就是第二基站在经历上次的基站切换后正在向第三基站转发下行报文，而在本次的切换过程中，识别到最新的状态是第二基站作为第三基站的目标基站，所以停止第二基站原先向第三基站转发下行报文的行为，减少下行报文冗余的中转路径。
其他场景不允许UE XnAP ID重复。UE XnAP ID在切换过程中会一直被占用，直到基站执行UE Context Release才被回收重用。
以下以一次实际切换过程进行举例说明：参考图3所示的结构，以gNB1代表第一基站，以gNB2代表第二基站，以gNB3代表第三基站。
当UE从gNB1切换到gNB2，再切换到gNB3，由于N4链路异常，或gNB3与AMF间的N2断链，所以下行报文都是通过gNB1逐级转发到gNB3的，UE接入gNB3后，再空口发给UE。此时如果UE切回到gNB2，则：UE发起MR，触发跨站切换；gNB3向gNB2发起切换请求，gNB3通过UE切换路径的UE XnAP ID和对应小区的NCGI，得知该UE从gNB2切出再切入。针对本次切换，gNB3用上次该UE切入时的目标UE XnAP ID 6作为源UE XnAP ID向gNB2发送切换请求。gNB2收到切换请求信令后，解析出里面携带的源UE XnAP ID就是上次切出时目标基站分配的目标UE XnAP ID 6，且发送切换请求的小区NCGI也正是上次切出的目标小区，同时该UE上下文一直在，此时gNB2停止该UE报文下行转发，变更为本地存储。判断切入的UE是gNB2站正在下行转发的UE后，gNB2给gNB3回复切换请求信令。gNB3空口发送RRC重置指令通知UE切换至gNB2，此后上下行空口无数据。UE接入到gNB2，UE和gNB2进行上下行空口数据传输。另外，在这之后还可以包括：gNB2通知gNB3释放UE Context等全部关于该UE的信息。gNB3回收之前分配的UE XnAP ID，删除之前维持的UE XnAP ID和NCGI的映射表。
也就是说，UE反复在两个异常站点切换时，例如图3所示UE从gNB2切换到gNB3后，再次切回到gNB2，例如由于UE发送给gNB3的MR中最强小区是gNB2，gNB3比较后发现gNB2的NCGI正是上次接入的源基站。gNB3此时发起的切换请求消息中携带的源UE XnAP ID就用上次接入时分配的目标UE XnAP ID，这样gNB2比较本次切换请求gNB3NCGI与异常切换终端上次切出时目标基站的NCGI相同，再比较本次切换请求携带的UE XnAP ID与异常切换终端上次切出时目标基站gNB3分配目标UE XnAP ID相同，即相同NCGI，且相同UE XnAP ID，可识别该UE就是之前那个异常切换终端。此时结束下行报文转发，改为空口直传给终端，并通知本次切换的源站gNB3释放UE上下文。其中，具体数据收发过程可参考图5。
在一些例子中，接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：在需要断开连接的情况下，向所述第一基站发送释放UE的指令。例如，UE正在异常切换后的第二基站做业务，若需要释放UE，则第二基站通知第一基站释放该UE，并清空本地该UE上下文等信息；若UE正在切换后的第三基站做业务，需要释放该UE，第三基站根据切换进出的映射表，先通知第二基站释放该UE，第二基站传递该信令到第一基站后再本地清空该UE上下文等信息，第一基站也执行此操作，直至第一个切换异常的基站收到释放命令为止。 也就是需要从最后一个目标基站起，逐级下行报文转发路径上的上一级基站送释放UE的指令，直至第一个源基站收到该释放指令为止，其中，由于跨站切换流程异常可以仅由目标基站引起，此处所述第一个源基站并不限定其状态异常与否。
在一些例子中，所述需要断开连接的情况，包括：所述第二基站检测到与所述UE无线链路失败；或收到所述UE向所述第二基站发送的重建请求。其中，此处的第二基站代表正在与UE正在连接并做业务的基站，也就是切换过程中最后一个目标基站。需要断开的情况可能由正在与UE连接的目标基站自主检测到，例如因无线链路失败等原因；或UE存在其他原因需要断开，则会主动发起RRC重建流程。在目标基站收到RRC重建流程时，先向上级基站发起UE释放流程(UE Context Release)，中转基站收到UE Context Release消息后转发给下行报文转发路径上的上一级基站，然后释放该UE的上下文等信息，直到UE Context Release消息传递到最初切换失败的源基站。
在一些例子中，接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：向第三基站发送切换请求；在收到所述核心网反馈的所述核心网与所述第三基站连接正常的指令的情况下，结束向所述第三基站转发下行报文；其中，所述核心网反馈的指令通过所述第一基站获取。也就是在第三基站与核心网的连接正常的情况下，第一基站会收到核心网反馈的连接正常的指令，不需要沿下行报文转发路径向第三基站转发下行报文，下行报文转发路径可以由前述映射表体现；在下行报文转发路径上，作为第三基站的上级的第二基站，会收到第一基站逐级转发的所述连接正常的指令，即不再向第三基站转发下行报文；由第三基站直接与核心网和UE之间进行上下文数据的交互，不需要保持之前切换过程中建立的下行报文转发过程。其中，第一基站和第二基站之间允许存在多个中转基站。
另外，在第三基站与核心网之间连接正常的情况下，作为下行报文转发路径中第三基站的上一级的第二基站，会收到第三基站发送的UE Context Release，从而释放该UE的上下文信息，并将该释放指令逐级转发至第一基站，供第一基站执行UE释放。
为便于进行理解，按照图3所示的执行环境举例如下：在本例中，与核心网连接正常的基站为gNB4(N2，N4链路可用)，即gNB4指代为上述与核心网之间连接正常的第三基站，gNB3指代与核心网之间连接正常的第三基站的上一级的第二基站，gNB1指代切换异常的首个基站，即第一基站，gNB2指代第一基站与第二基站之间，虽未提到但允许存在的其他中转基站。
最后一个目标基站为gNB4。UE发起MR，触发跨站切换；gNB3向gNB4发起切换请求；gNB4根据自身接纳拥塞处理算法，在资源允许的情况下接纳该UE，回复允许切换请求信令；gNB3发送RRC重置指令通知UE执行切换，此后上下行空口无数据；UE接入到gNB4，此时UE和gNB4进行上下行空口数据传输；gNB4作为目标基站发起Path Switch Request给AMF；AMF，SMF和UPF交互路径改变流程，UPF发送End Marker通知gNB1下行数据转发结束，gNB1根据之前维持的UE XnAP ID和切出目标小区NCGI，转发End Marker给gNB2，gNB2根据之前维持的UE XnAP ID和切出目标小区NCGI，再转给gNB3，gNB3再转给gNB4，后续下行报文直接从UPF到gNB4，gNB4空口发送到UE。
当gNB4通过N2收到AMF的连接正常反馈(PATH SWITCH REQUEST ACKNOWLEDGE)时；gNB4发送UE Context Release通知gNB3释放该UE上下文信息。gNB3转发此信令给gNB2，同时本地释放UE上下文相关的空口和控制面部分，如有下行数 据转发还要继续，如转发完毕，全部清空该UE信息，回收之前分配的UE XnAP ID，删除之前维持的UE XnAP ID和NCGI的映射表。gNB2转发UE Context Release信令给gNB1，同时本地释放UE Context相关的空口和控制面部分，如有下行数据转发还要继续，如转发完毕，全部清空该UE信息，回收之前分配的UE XnAP ID，删除之前维持的UE XnAP ID和NCGI的映射表。gNB1本地释放UE Context相关的空口和控制面部分，如有下行数据转发还要继续，如转发完毕，全部清空该UE信息，回收之前分配的UE XnAP ID，删除之前维持的UE XnAP ID和NCGI的映射表。
即，如果UE移动到与核心网连接链路正常的基站如图3中的gNB4时，该基站发起的路径变更请求Path Switch Request流程成功。核心网用户面网元(如UPF)会改变下行路径到当前基站(gNB4)，并发送End Marker通知最初的源基站，逐级停止下行报文的转发过程。目标基站如图3中的gNB4向上级基站gNB3发起UE Context Release，gNB3作为中转基站传递UE Context Release给上级基站gNB2后，清空本地该UE的上下文。gNB2作为作为中转基站传递UE Context Release给上级基站gNB1后，清空本地该UE的上下文。gNB1作为最初的源基站收到UE Context Release后，如果End Marker发完，释放该UE全部信息。具体数据传送过程可参考图6。
在本申请实施方式中，在接收第一基站的切换请求后，若第二基站与核心网之间的连接异常，保持UE不释放，最初链路异常的源基站可持续将下行报文转发给下一个基站，比如通过第一基站转发到第二基站，也就是UE切换到的第二基站即使与核心网连接异常，也能够获取核心网的下行报文，使得UE在切换基站的过程中，不会与核心网产生断链的状态，保证UE移动过程中的的业务连接。若切换的过程中，存在目标基站与核心网的连接状态正常的情况，则在切换成功后，之前所建立的下行报文转发路径停止进行下行报文的转发，路径上的基站均释放UE，仅保留该目标基站、核心网、UE之间的信息传输路径；即切入正常基站后，触发之前路径的释放，减少资源占用。另外，在两个连接异常的基站来回切换时识别反复切换，减少下行报文冗余的中转路径。
上面各种方法的步骤划分，只是为了描述清楚，实现时可以合并为一个步骤或者对某些步骤进行拆分，分解为多个步骤，只要包括相同的逻辑关系，都在本专利的保护范围内；对算法中或者流程中添加无关紧要的修改或者引入无关紧要的设计，但不改变其算法和流程的核心设计都在该专利的保护范围内。
本申请一个实施方式涉及一种基站，如图7所示，包括：
响应模块201，用于响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；
连接模块202，用于根据所述UE的身份标识与所述UE建立连接；
处理模块203，用于在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。
对于响应模块201，所述切换请求中携带用户设备UE的身份标识，例如：所述切换请求中携带所述第一基站分配给所述UE的身份标识；所述响应第一基站的切换请求，例如：保存所述第一基站的身份标识和所述第一基站分配给所述UE的身份标识；将所述第二基站的身份标识和所述第二基站分配给所述UE的身份标识发送至所述第一基站。
对于处理模块203，所述连接异常的情况，例如：与核心网的控制面网元连接异常；或 收到核心网发送的路径变更失败消息。
在一个例子中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：响应第三基站发送的切换请求，所述第三基站的切换请求中携带所述第三基站分配给所述UE的身份标识和所述第三基站的身份标识；在根据所述第三基站的身份标识确定所述第三基站为上次异常切换时响应第二基站的切换请求的基站，且所述第三基站为所述UE分配的身份标识为上次异常切换时响应第二基站的切换请求的基站为所述UE分配的身份标识的情况下，停止向所述第三基站转发所述核心网下发的下行报文；通知所述第三基站释放所述UE的上下文。
在一个例子中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：在需要断开连接的情况下，向所述第一基站发送释放UE的指令。
在一个例子中，所述需要断开连接的情况，包括：所述第二基站检测到与所述UE无线链路失败；或收到所述UE向所述第二基站发送的重建请求。
在一个例子中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：向第三基站发送切换请求；在收到所述核心网反馈的所述核心网与所述第三基站连接正常的指令的情况下，结束向所述第三基站转发下行报文；其中，所述核心网反馈的指令通过所述第一基站获取。
本实施方式中，在接收第一基站的切换请求后，若第二基站与核心网之间的连接异常，保持UE不释放，最初链路异常的源基站可持续将下行报文转发给下一个基站，比如通过第一基站转发到第二基站，也就是UE切换到的第二基站即使与核心网连接异常，也能够获取核心网的下行报文，使得UE在切换基站的过程中，不会与核心网产生断链的状态，保证UE移动过程中的的业务连接。
不难发现，本实施方式为与上述实施方式相对应的系统实施例，本实施方式可与上述实施方式互相配合实施。上述实施方式中提到的相关技术细节在本实施方式中依然有效，为了减少重复，这里不再赘述。相应地，本实施方式中提到的相关技术细节也可应用在上述实施方式中。
值得一提的是，本实施方式中所涉及到的各模块均为逻辑模块，在实际应用中，一个逻辑单元可以是一个物理单元，也可以是一个物理单元的一部分，还可以以多个物理单元的组合实现。此外，为了突出本申请的创新部分，本实施方式中并没有将与解决本申请所提出的技术问题关系不太密切的单元引入，但这并不表明本实施方式中不存在其它的单元。
本申请一个实施方式涉及一种基站，如图8所示，包括至少一个处理器301；以及，与所述至少一个处理器301通信连接的存储器302；其中，所述存储器302存储有可被所述至少一个处理器301执行的指令，所述指令被所述至少一个处理器执行，以使所述至少一个处理器能够执行上述的基站切换方法。
其中，存储器和处理器采用总线方式连接，总线可以包括任意数量的互联的总线和桥，总线将一个或多个处理器和存储器的各种电路连接在一起。总线还可以将诸如外围设备、稳压器和功率管理电路等之类的各种其他电路连接在一起，这些都是本领域所公知的，因此，本文不再对其进行进一步描述。总线接口在总线和收发机之间提供接口。收发机可以是一个元件，也可以是多个元件，比如多个接收器和发送器，提供用于在传输介质上与各种其他装置通信的单元。经处理器处理的数据通过天线在无线介质上进行传输，进一步，天线还接收 数据并将数据传送给处理器。
处理器负责管理总线和通常的处理，还可以提供各种功能，包括定时，外围接口，电压调节、电源管理以及其他控制功能。而存储器可以被用于存储处理器在执行操作时所使用的数据。
本申请一个实施方式涉及一种计算机可读存储介质，存储有计算机程序。计算机程序被处理器执行时实现上述方法实施例。
即，本领域技术人员可以理解，实现上述实施例方法中的全部或部分步骤是可以通过程序来指令相关的硬件来完成，该程序存储在一个存储介质中，包括若干指令用以使得一个设备(可以是单片机，芯片等)或处理器(processor)执行本申请各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(ROM，Read-OnlyMemory)、随机存取存储器(RAM，RandomAccessMemory)、磁碟或者光盘等各种可以存储程序代码的介质。
本领域的普通技术人员可以理解，上述各实施方式是实现本申请的具体实施例，而在实际应用中，可以在形式上和细节上对其作各种改变，而不偏离本申请的精神和范围。

Claims (11)

  1. 一种基站切换方法，应用于第二基站，包括：
    响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；
    根据所述UE的身份标识与所述UE建立连接；
    在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。
  2. 根据权利要求1所述的基站切换方法，其中，所述连接异常的情况包括：
    与核心网的控制面网元连接异常；
    或收到核心网发送的路径变更失败消息。
  3. 根据权利要求1所述的基站切换方法，其中，所述切换请求中携带用户设备UE的身份标识，包括：
    所述切换请求中携带所述第一基站分配给所述UE的身份标识；
    所述响应第一基站的切换请求，包括：
    保存所述第一基站的身份标识和所述第一基站分配给所述UE的身份标识；
    将所述第二基站的身份标识和所述第二基站分配给所述UE的身份标识发送至所述第一基站。
  4. 根据权利要求3所述的基站的切换方法，其中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：
    向第三基站发送切换请求，所述向第三基站发送的切换请求中携带所述第二基站分配给所述UE的身份标识和所述第二基站的身份标识；
    在将所述UE切换至所述第三基站后，将所述第一基站转发的所述下行报文转发给所述第三基站。
  5. 根据权利要求4所述的基站切换方法，其中，所述将所述UE切换至所述第三基站之后，还包括：
    响应第四基站发送的切换请求，所述第四基站的切换请求中携带所述第四基站分配给UE的身份标识和所述第四基站的身份标识；
    在根据所述第四基站的身份标识和所述第四基站分配给所述UE的身份标识，确定所述第四基站为所述第三基站，所述UE相同的情况下，停止向所述第三基站转发所述下行报文；
    通知所述第三基站释放所述UE的上下文。
  6. 根据权利要求1所述的基站切换方法，其中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：
    在需要断开连接的情况下，向所述第一基站发送释放UE的指令。
  7. 根据权利要求6所述的基站切换方法，其中，所述需要断开连接的情况，包括：
    所述第二基站检测到与所述UE无线链路失败；
    或收到所述UE向所述第二基站发送的重建请求。
  8. 根据权利要求1所述的基站切换方法，其中，所述接收所述第一基站转发的来自核心网的所述UE的下行报文之后，包括：
    向第三基站发送切换请求；
    在收到所述核心网反馈的所述核心网与所述第三基站连接正常的指令的情况下，结束向所述第三基站转发下行报文；其中，所述核心网反馈的指令通过所述第一基站获取。
  9. 一种基站，包括：
    响应模块，用于响应第一基站的切换请求，所述切换请求中携带用户设备UE的身份标识和所述第一基站的身份标识；
    连接模块，用于根据所述UE的身份标识与所述UE建立连接；
    处理模块，用于在与核心网存在连接异常的情况下，不释放所述UE，接收所述第一基站转发的来自核心网的所述UE的下行报文。
  10. 一种基站，包括：
    至少一个处理器；以及，
    与所述至少一个处理器通信连接的存储器；其中，
    所述存储器存储有可被所述至少一个处理器执行的指令，所述指令被所述至少一个处理器执行，以使所述至少一个处理器能够执行如权利要求1至8中任一项所述的基站切换方法。
  11. 一种计算机可读存储介质，存储有计算机程序，其中，所述计算机程序被处理器执行时实现权利要求1至8中任一项所述的基站切换方法。
PCT/CN2022/130975 2021-11-10 2022-11-09 基站切换方法、基站和计算机可读存储介质 WO2023083228A1 (zh)

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CN110167082A (zh) * 2018-02-14 2019-08-23 中兴通讯股份有限公司 网络的切换方法、装置及系统，切换确定方法及装置

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CN102802220A (zh) * 2011-05-25 2012-11-28 华为技术有限公司 切换方法和基站
US20150087268A1 (en) * 2012-03-29 2015-03-26 Mitsubishi Electric Corporation Trust based system and method for performing a handover from a source base station to a target base station
CN105474702A (zh) * 2014-03-14 2016-04-06 华为技术有限公司 切换方法、终端、基站及系统
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