CN113163440B

CN113163440B - Establishment method of forward interface, UE access method, UE switching method and device

Info

Publication number: CN113163440B
Application number: CN202110425791.2A
Authority: CN
Inventors: 许丽香; 王弘; 柯小婉; 汪巍崴
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2017-05-05
Filing date: 2017-06-16
Publication date: 2021-11-30
Anticipated expiration: 2037-06-16
Also published as: CN109246747B; CN109246747A; CN113163440A

Abstract

The application discloses a method and a device for switching UE among different DUs, wherein a method executed by a centralized unit CU of a base station gNB is provided, the gNB comprises the CU and a plurality of distribution units DU, and the method comprises the following steps: identifying a target DU among the plurality of DUs based on a measurement report message associated with a terminal; sending a first message to the identified target DU for establishing a context associated with the terminal at the identified target DU, the first message including a first identity allocated by the CU for the terminal; receiving a second message from the identified target DU as a response to the first message, the second message including a first identity allocated by the CU to the terminal and a second identity allocated by the target DU to the terminal; and transmitting a third message to a source DU of the plurality of DUs, the third message including a radio resource control, RRC, reconfiguration message and information for stopping data transmission related to the terminal.

Description

Establishment method of forward interface, UE access method, UE switching method and device

The application is a divisional application of patent applications with application dates 2017, 16/06/78, application number 201710458428.4, and invention names 'establishment method of forward interface, UE access method, UE switching method and device'.

Technical Field

The present application relates to wireless communication technologies, and in particular, to a method for establishing a forward interface, a method for accessing a UE, a method for switching a UE, and an apparatus for switching a UE.

Background

Modern mobile communications are increasingly tending to provide higher mobile bandwidth, less latency, support a large number of terminal services, as shown in fig. 1, which is a system architecture diagram of a next generation network or a fifth generation (5G) network. Wherein:

a User Equipment (UE)101 is a terminal device for receiving data.

The next generation radio access network (NG-RAN)102 is a radio access network including base stations (gbbs or enbs connected to a 5G core network (5 GC)) that provide access to radio network interfaces for UEs.

An access control and mobility management function (AMF)103 is responsible for managing the mobility context and security information of the UE.

A user plane functional entity (UPF)104 mainly provides the functions of the user plane.

A Session Management Function (SMF)105 is responsible for session management.

The Data Network (DN)106 contains services such as the operator, access to the internet, and services for third parties.

To support network function virtualization, enabling more efficient resource management and scheduling, the gNB in 5G may be further divided into a centralized unit (gNB-CU) and a distributed unit (gNB-DU). Hereinafter, referred to as CU and DU in the present invention. Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) functions are in the CU. The functions of RLC (radio link control), MAC (medium access control) and physical layer are in the DU. Between CU and DU is a standardized public interface F1. The F1 interface is divided into a control plane (F1-C) and a user plane (F1-U). The transport network layer of F1-C is based on IP transport. For more reliable transport signaling, Stream Control Transmission Protocol (SCTP) protocol is added on top of IP. The application layer protocol of the F1 interface is F1 AP. SCTP can provide reliable application layer message transport. The transport layer of F1-U is the user datagram protocol/Internet protocol (UDP/IP), and the GPRS tunneling protocol user plane (GTP-U) is used above UDP/IP to carry user plane Protocol Data Units (PDUs).

As can be seen from the above prior art, the architecture of 5G is different from that of LTE, and a forward interface needs to be supported inside a base station in 5G. How to support UE access, call setup and handover, etc. at the F1 interface has not been discussed in detail at present.

Disclosure of Invention

The application provides several establishing methods of a forward interface, a UE access method, a UE switching and communication method and devices, so as to realize better intercommunication between DU and CU.

The application provides a method for establishing a forward interface, which comprises the following steps:

the base station concentration unit CU receives a forward interface F1 setup request message from the base station distribution unit DU;

the CU sends an F1 setup response message to the DU.

Preferably, the F1 setup request message includes one or more of the following information: DU identification, an information list of a service cell on the DU, and capability information of the DU;

the F1 establishment response message comprises one or more of the following information: CU identification, public land mobile network PLMN identification list supported by CU, and cell configuration list.

Preferably, the information of the serving cell in the information list of the serving cell on the DU includes one or more of the following information: cell identification, frequency information of a cell, uplink transmission bandwidth, downlink transmission bandwidth information, physical cell identification, Tracking Area Identification (TAI) or Tracking Area Code (TAC), broadcasted PLMN identification list, Transmission Receiving Point (TRP) information, Beam information, physical channel information in the cell, transmission channel information in the cell, logical channel information in the cell, and cell access layer (AP) identification which is distributed by the DU and used for an F1 interface; and/or the presence of a gas in the gas,

the cell configuration information in the cell configuration list comprises one or more of the following information: a cell identifier, configuration information of a common channel in the cell, system information in the cell, scheduling information sent by the system information, and a cell AP identifier allocated by the CU and used for an F1 interface.

Preferably, when the F1 setup request message includes capability information of the DU, the method includes: and the CU schedules the user terminal UE by using the capability information of the DU.

Preferably, when the F1 setup response message does not include the cell configuration list, after the CU sends the F1 setup response message to the DU, the method includes:

CU sends a cell establishment request message to DU, and the cell establishment request message carries cell configuration information of a cell to be configured; the CU receives a cell establishment response message sent by the DU;

wherein the cell configuration information comprises one or more of the following information: a cell identifier, configuration information of a common channel in the cell, system information in the cell, scheduling information sent by the system information, and a cell AP identifier allocated by the CU and used for an F1 interface.

Preferably, if the cell establishment request message and/or the cell establishment response message is sent through a cell signaling connection, the cell establishment request message and/or the cell establishment response message does not include a cell identifier.

Preferably, when the cell configuration information does not include the system information in the cell and/or the scheduling information sent by the system information, the method includes: and sending a system information transmission message to the DU by one or more cells correspondingly established by the CU, wherein the system information transmission message comprises a cell identifier, system information in the cell and/or scheduling information sent by the system information.

The application also provides a method for establishing the forward interface, which comprises the following steps:

the DU sends F1 establishment request message to the CU;

the DU receives F1 setup response messages from the CUs.

the F1 establishment response message comprises one or more of the following information: CU identification, PLMN identification list supported by CU and cell configuration list.

The present application also provides a CU apparatus for forward interface establishment, the apparatus comprising: a transmitting unit and a receiving unit;

the receiving unit is configured to receive an F1 setup request message from the DU; wherein, the F1 establishment request message includes one or more of the following information: DU identification, an information list of a service cell on the DU, and capability information of the DU;

the sending unit is configured to send an F1 setup response message to the DU; wherein, the F1 setup response message includes one or more of the following information: CU identification, PLMN identification list supported by CU and cell configuration list.

The present application further provides a DU apparatus for establishing a forward interface, where the apparatus includes: a transmitting unit and a receiving unit;

the sending unit is used for sending an F1 establishment request message to the CU; wherein, the F1 establishment request message includes one or more of the following information: DU identification, an information list of a service cell on the DU, and capability information of the DU;

the receiving unit is used for receiving an F1 establishment response message from the CU; wherein, the F1 setup response message includes one or more of the following information: CU identification, PLMN identification list supported by CU and cell configuration list.

CU sends F1 establishment request message to DU;

the CU receives F1 setup response message from the DU.

Preferably, the F1 setup request message includes one or more of the following information: CU identification, PLMN identification list supported by CU, information list of service cell on DU, and cell configuration list;

the F1 establishment response message comprises one or more of the following information: DU identity, DU capability information, and cell actual configuration information.

the DU receives F1 setup request messages from CUs;

the DU sends an F1 setup response message to the CU.

the sending unit is configured to send an F1 establishment request message to the DU; wherein, the F1 establishment request message includes one or more of the following information: CU identification, PLMN identification list supported by CU, information list of service cell on DU, and cell configuration list;

the receiving unit is configured to receive an F1 setup response message from the DU; wherein, the F1 setup response message includes one or more of the following information: DU identity, DU capability information, and cell actual configuration information.

The present application further provides a DU apparatus for establishing a forward interface, the apparatus including: a transmitting unit and a receiving unit;

the receiving unit is used for receiving an F1 establishment request message from the CU to the DU; wherein, the F1 establishment request message includes one or more of the following information: CU identification, PLMN identification list supported by CU, information list of service cell on DU, and cell configuration list;

the sending unit is used for sending an F1 establishment response message to the CU; wherein, the F1 setup response message includes one or more of the following information: DU identity, DU capability information, and cell actual configuration information.

CU sends F1 setup request message to DU; wherein, the F1 creates a demand message containing one or more of the following information: CU identification, PLMN identification list supported by CU, and information list of service cell on DU;

the CU receives an F1 setup request message from the DU; wherein, the F1 establishment request message includes one or more of the following information: DU identification, an information list of a service cell on the DU, and capability information of the DU;

the CU sends an F1 establishment response message to the DU; wherein, the F1 setup response message includes one or more of the following information: a list of PLMN identities supported by the CU, a list of cell configurations.

Preferably, when the F1 setup request message includes the information list of the serving cell on the DU, the F1 setup request message does not include the information list of the serving cell on the DU; and/or the presence of a gas in the gas,

when the F1 creates a demand message containing a list of PLMN identities supported by a CU, the F1 creates a response message not containing a list of PLMN identities supported by the CU.

Preferably, when the application layer information of the DU is updated, the method includes: the CU receives DU configuration update information sent by the DU, and the DU configuration update information comprises updated DU application layer information; and/or the presence of a gas in the gas,

when the application layer information of the CU is updated, the method comprises the following steps: and the CU sends CU configuration updating information to the DU, and the CU configuration updating information carries updated CU application layer information.

Preferably, after receiving the updated DU application layer information, if the system information needs to be updated, the CU sends the updated system information and/or the scheduling information of the updated system information to the DU.

Preferably, the updated system information and/or the scheduling information of the updated system information is carried in a system information update message or a DU configuration update response message.

the DU receives F1 setup request messages from CUs;

the DU sends F1 establishment request message to the CU;

the DU receives the F1 setup response message sent by the CU.

Preferably, the F1 establishment request message includes one or more of the following information: CU identification, PLMN identification list supported by CU, and information list of service cell on DU;

the F1 establishment request message comprises one or more of the following information: DU identification, an information list of a service cell on the DU, and capability information of the DU;

the F1 establishment response message comprises one or more of the following information: a list of PLMN identities supported by the CU, a list of cell configurations.

the sending unit is configured to send an F1 establishment request message to the DU, and is further configured to send an F1 establishment response message to the DU after the receiving unit receives the F1 establishment request message;

the receiving unit is configured to receive an F1 setup request message from the DU;

wherein, the F1 creates a demand message containing one or more of the following information: CU identification, PLMN identification list supported by CU, and information list of service cell on DU;

the receiving unit is used for receiving an F1 establishment demand message from a CU; further configured to receive an F1 setup response message from the CU after the sending unit sends the F1 setup request message;

the sending unit is used for sending an F1 establishment request message to the CU;

The application also provides a UE access method, which comprises the following steps:

the DU receives a Radio Resource Control (RRC) connection request message from the UE;

the DU sends an initial UE message transmission message to the CU through a user plane channel or a control plane channel between the DU and the CU;

the DU receives a radio bearer configuration request message from a CU;

the DU configures resources according to the received information and sends a radio bearer configuration response message to the CU;

the DU receives a downlink RRC transmission message from the CU;

the DU forwards the received RRC connection establishment message to the UE;

the DU receives an RRC connection setup complete message from the UE;

and the DU sends the received RRC connection establishment completion message to the CU through a control plane or a user plane.

Preferably, the initial UE message transmission message includes one or more of the following information: DU is distributed for the UE and the distribution unit user equipment access layer protocol identification DU UE AP ID, DU receives the cell identification of the cell of the RRC connection request message, TAI, the RRC connection request message, DU is distributed for the UE cell radio network temporary identification C-RNTI;

and/or, the radio bearer configuration request message includes one or more of the following information: CU UE AP ID distributed by CU for the UE, DU UE AP ID distributed by DU for the UE, cell identification of the UE, radio bearer RB information to be configured, configuration information of a physical channel, configuration information of a transmission channel, configuration information of a logical channel and uplink channel information;

and/or, the radio bearer configuration response message contains one or more of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, RB information configured for UE, and C-RNTI distributed by DU for UE;

and/or, the downlink RRC transmission message includes one or more of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, RRC connection establishment message, logical channel information and uplink channel information for sending RRC message, and C-RNTI distributed by CU for UE;

and/or when the DU sends the RRC connection setup completion message to the CU, sending one or more of the following information to the CU: CU is the CU UE AP ID distributed by the CU for the UE, and DU is the DU UE AP ID distributed by the UE.

Preferably, when a session does not need to be established, the DU receives a downlink NAS transport message sent by an AMF (access control and mobility management function) entity from the CU through a control plane channel or a user plane channel, and forwards the downlink NAS transport message to the UE;

when a session needs to be established, the DU receives a radio bearer reconfiguration request message from the CU, the radio bearer reconfiguration request message including one or more of the following information in combination: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, RB information to be added, RB information to be reconfigured and RB information to be deleted; the DU allocates resources and sends a rb reconfiguration response message to the CUs, where the rb reconfiguration response message contains one or more of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, and configuration information of RB; the DU receives the RRC connection reconfiguration message from the CU and sends the RRC connection reconfiguration message to the UE; and the DU sends the RRC connection reconfiguration completion message sent by the UE to the CU through a control plane or a user plane.

Preferably, RRC messages between the DU and the CU are transported over the control plane, or RRC messages on the signaling radio bearer SRB0 are transported over the control plane, and RRC messages on the other SRBs are transported over the user plane;

the user plane channel for transmitting RRC message is established between DU and CU by the following three ways:

the first method is as follows: when DU receives RRC connection request message from UE, DU distributes down channel information and sends the distributed down channel information to CU through initial UE message transmission message, CU distributes up channel information and sends the distributed up channel information to DU through wireless load configuration message; the downlink channel information and the uplink channel information comprise a channel identification TEID and/or a transport layer address.

The second method comprises the following steps: when the DU receives the RRC connection request message from the UE, the DU allocates downlink channel information, the allocated downlink channel information is sent to the CU through an initial UE message transmission message, after the DU sends a radio bearer configuration response message to the CU, the CU allocates uplink channel information, and the allocated uplink channel information is sent to the DU through a downlink RRC transmission message; the downlink channel information and the uplink channel information comprise a channel identification TEID and/or a transport layer address.

The third method comprises the following steps: after the DU sends an initial UE message transmission message to the CU, the CU allocates uplink channel information, the allocated uplink channel information is sent to the DU through a radio bearer configuration message, the DU allocates downlink channel information, and the allocated downlink channel information is sent to the CU through a radio bearer configuration response message; the downlink channel information and the uplink channel information comprise channel identification TEID and/or transport layer address;

the RRC messages on the corresponding SRBs 0 are transmitted through the control plane, the RRC messages on the other SRBs are transmitted through the user plane, and the RRC messages on the other SRBs are transmitted through the same user plane channel, or a user plane channel is established corresponding to each SRB for transmission, and correspondingly, the allocated uplink or downlink channel information corresponds to each SRB.

Preferably, the RB information to be added includes one or more of the following information in combination: an RB identifier, configuration information of a physical channel of the RB, configuration information of a transmission channel of the RB, configuration information of a logical channel of the RB, QoS Flow information mapped on the RB and/or uplink channel information of the RB; the QoS Flow information mapped on the RB comprises a Flow identifier and Qos information corresponding to Flow;

and/or the uplink channel information comprises a transport layer address and an uplink TEID;

and/or, the RB information to be reconfigured includes one or more of the following information in combination: an RB identity, reconfiguration information of a physical channel of the RB, reconfiguration information of a transport channel of the RB, reconfiguration information of a logical channel of the RB, QoS Flow information to be added on the RB, QoS Flow information to be deleted on the RB, and/or QoS Flow information to be transmitted on the RB. The QoS Flow information to be added on the RB comprises a Qos Flow identifier and Qos Flow Qos information; the QoS Flow information to be reconfigured on the RB comprises a Qos Flow identifier and a Qos parameter to be reconfigured; and the QoS Flow information to be deleted on the RB comprises a Qos Flow identifier.

The application also provides an access method of the UE, which comprises the following steps:

a CU receives an RRC connection request message forwarded by a DU from UE through a user plane channel or a control plane channel between the CU and the DU;

the CU sends a radio bearer configuration request message to the DU; wherein, one or more combinations of the following information are contained in the radio bearer configuration request message: CU UE AP ID distributed by CU for the UE, DU UE AP ID distributed by DU for the UE, cell identification of the UE, RB information to be configured, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel and uplink channel information;

the CU sends an RRC connection establishment message to the DU through a user plane channel or a control plane channel between the CU and the DU, and receives an RRC connection establishment completion message which is forwarded from the UE by the DU through the user plane channel or the control plane channel between the CU and the DU;

when a session does not need to be established, the CU receives downlink NAS transmission information sent by the AMF, and sends RRC message downlink NAS transmission to the DU through a control plane channel or a user plane channel;

when a session needs to be established, the CU receives an initial context setup request message from the AMF, and sends a radio bearer reconfiguration request message to the DU, where the radio bearer reconfiguration request message includes one or more of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, RB information to be added, RB information to be reconfigured and RB information to be deleted; receiving a radio bearer reconfiguration response message from the DU, the radio bearer reconfiguration response message containing a combination of one or more of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, and configuration information of RB; and sending an RRC connection reconfiguration message to the DU, and receiving an RRC connection reconfiguration completion message sent by the UE forwarded by the DU.

The present application further provides a DU device for UE access, the device including: a receiving unit, a transmitting unit and a processing unit;

the receiving unit is configured to receive an RRC connection request message sent by a user equipment UE;

the sending unit is configured to send the RRC connection request message to a CU through a user plane channel or a control plane channel between the sending unit and the CU;

the processing unit is configured to receive the radio bearer configuration request message sent by the CU, configure resources according to the received information, receive an RRC connection setup message sent by the CU through the user plane channel or the control plane channel, and forward the RRC connection setup message to the UE; the system is further configured to receive an RRC connection setup complete message sent by the UE, send the RRC connection setup complete message to the CU through the user plane channel or the control plane channel, and include an identifier of the UE in a data packet header of the corresponding user plane channel or the control plane channel; the UE is also used for receiving RRC message downlink NAS transmission sent by the CU according to the downlink NAS transmission message of the AMF through a control plane channel or a user plane channel when the session does not need to be established, and forwarding the RRC message downlink NAS transmission to the UE;

wherein, one or more combinations of the following information are contained in the radio bearer configuration request message: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU for UE, cell identification of UE, RB information to be configured, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel and uplink channel information.

The present application also provides a CU apparatus for UE access, the apparatus comprising: a receiving unit, a transmitting unit and a processing unit;

the receiving unit is configured to receive, through a user plane channel or a control plane channel between the DU, an RRC connection request message forwarded by the DU from the UE;

the sending unit is configured to send a radio bearer configuration request message to the DU; wherein, one or more combinations of the following information are contained in the radio bearer configuration request message: CU UE AP ID distributed by CU for the UE, DU UE AP ID distributed by DU for the UE, cell identification of the UE, RB information to be configured, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel and uplink channel information;

the processing unit is configured to send an RRC connection setup message to the DU through the user plane channel or the control plane channel, receive an RRC connection setup complete message forwarded from the UE by the DU through the user plane channel or the control plane channel, and include an identifier of the UE in a packet header of the user plane channel or the control plane channel for carrying the RRC connection setup complete message; and the ue is further configured to receive a downlink NAS transport message sent by the AMF when a session does not need to be established, and send an RRC message downlink NAS transport to the DU through a control plane tunnel or a user plane tunnel.

The application also provides a method for switching the UE, wherein the source DU and the destination DU of the switching correspond to the same CU, and the method comprises the following steps:

a CU receives a measurement report message sent to a base station by UE through a user plane channel or a control plane channel between the CU and a source DU;

after determining to switch the UE, the CU sends a radio bearer configuration message to a target DU; wherein the radio bearer configuration message contains one or more of the following information: CU allocates CU UE AP ID for UE, UE context information in S-DU, target cell identification, RB information to be configured, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel, uplink channel information and MBB switching indication;

the CU receives a radio bearer configuration response message sent by the target DU; including in the radio bearer configuration response message one or more combinations of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by target DU for UE, and RB information configured for UE;

the CU sends RRC connection reconfiguration information to the source DU through the user plane channel or the control plane channel, and sends information of switching between different DUs and/or an MBB instruction to the source DU;

the CU sends data to the target DU, and after the UE is synchronized to a target cell, the CU receives an RRC connection establishment completion message sent by the target DU through a user plane channel or a control plane channel; the RRC connection setup complete message is sent by the UE to the base station;

the CU sends a UE context release message to the source DU.

Preferably, RRC messages between the DU and the CUs are transported over the control plane, or RRC messages on the signaling radio bearer SRB0 are transported over the control plane and RRC messages on the other SRBs are transported over the user plane.

Preferably, the RRC messages on the corresponding SRB0 are transmitted through the control plane, the RRC messages on the other SRBs are transmitted through the user plane, and the RRC messages on the other SRBs are transmitted through the same user plane channel, or a user plane channel is established corresponding to each SRB for respective transmission, and correspondingly, the allocated uplink or downlink channel information corresponds to each SRB.

Preferably, the rb configuration message includes, for each DRB, CU allocated uplink channel information; corresponding to the method that other RRC messages except SRB0 are transmitted through a user plane, the radio bearer configuration message contains the uplink channel information distributed by the CU for the SRB, and the communication information is a channel which corresponds to each SRB or is common to the transmission of the RRC messages on all the SRBs except SRB 0; the uplink channel information comprises a transport layer address and a TEID;

and/or the RB information configured for the UE comprises configuration information of SRB and DRB; corresponding to each DRB, the message contains downlink channel information distributed by the T-DU; a method for transmitting other RRC messages except SRB0 through a user plane, wherein the messages comprise downlink channel information distributed by T-DU for SRB, and the communication information is a channel which is corresponding to each SRB or is common to RRC message transmission on all SRBs except SRB 0; the channel information includes a transport layer address and a TEID.

Preferably, the sending, by the CU, the information about switching between different DUs and/or the indication of the MBB to the source DU includes: the CU sends the information of the handover between different DUs and/or the indication of the MBB through an F1AP message, or includes the information of the handover between different DUs and/or the indication of the MBB in a packet header of a user plane channel used for carrying the RRC connection reconfiguration message and sends the packet header to the source DU.

Preferably, when the information about the switching between the different DUs and/or the indication of the MBB is included in a data packet header of the user plane channel, the data packet header further includes a CU UE AP ID allocated by the CU for the UE, a DU UE AP ID allocated by the S-DU for the UE, and/or logical channel information for sending the RRC connection reconfiguration message.

Preferably, when the switch is an MBB switch, the method includes: the CU decides the time to stop sending downlink data or stop communicating with the UE and informs the source DU.

Preferably, the sending, by the CU, data to the destination DU includes:

the CU sends the data which is not confirmed by the UE and received from the UPF to the target DU, wherein the data is PDCP PDU; alternatively, the first and second electrodes may be,

if the T-DU and the S-DU have the same RB configuration, the CU sends data which is not confirmed by the UE and is received from the UPF to the target DU, the data is PDCP PDU, and the source DU sends RLC context of the source side to the target DU; corresponding to the PDCP PDU successfully sent by the part, the target DU only sends the RLC PDU which is not received by the UE to the UE; the CU receives an RLC context transfer message sent by the source DU; the CU sends an RLC context transfer two message to the target DU;

in the RLC context transfer one message and the RLC context transfer two message, including: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by source DU for UE, RLC sending state and/or PDCP sending and receiving state; wherein the RLC transmission state comprises the SN of the last successfully transmitted GTP-U data packet, the SN of the unsuccessfully transmitted GTP-U data packet and/or the unsuccessfully transmitted RLC SN.

a source DU receives a measurement report message from UE, and the source DU sends the measurement report message to a CU through a user plane channel or a control plane channel between the source DU and the CU;

the source DU receives RRC connection reconfiguration messages sent by the CU through the user plane channel or the control plane channel, and receives switching information and/or MBB (signaling message bus) instructions between different DUs;

and the source DU receives the UE context release message sent by the CU.

The present application also provides a CU apparatus for UE handover, the apparatus including: a transmitting unit, a processing unit and a receiving unit;

the receiving unit is configured to receive a measurement report message sent by the UE to the base station through a user plane channel or a control plane channel between the source DU and the UE;

the processing unit is configured to send a radio bearer configuration message to the destination DU after determining to switch the UE; the radio bearer configuration response message is also used for receiving the radio bearer configuration response message sent by the destination DU; the system is further configured to send an RRC connection reconfiguration message to the source DU through the user plane channel or the control plane channel, and send information of handover between different DUs and/or an indication of an MBB to the source DU; the UE is also used for sending data to the target DU, and receiving RRC connection establishment completion information sent by the target DU through a user plane channel after the UE is synchronized to a target cell; wherein the RRC connection setup complete message is sent by the UE to the base station;

the sending unit is configured to send a UE context release message to the source DU;

wherein the radio bearer configuration message contains one or more of the following information: CU allocates CU UE AP ID for UE, UE context information in S-DU, target cell identification, RB information to be configured, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel, uplink channel information and MBB switching indication; including in the radio bearer configuration response message one or more combinations of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by target DU for UE, and RB information configured for UE.

The present application further provides a source DU apparatus for UE handover, the apparatus including: a first processing unit, a second processing unit and a third processing unit;

the first processing unit is configured to receive a measurement report message sent by a user equipment UE, and further configured to send the measurement report message to a CU through a user plane channel or a control plane channel between the CU and the first processing unit;

the second processing unit is configured to receive, through the user plane channel or the control plane channel, an RRC connection reconfiguration message sent by the CU, and receive information about switching between different DUs and/or an indication of an MBB;

and the third processing unit is configured to receive a UE context release message sent by the CU.

The present application further provides a destination DU device for UE handover, the device including: a first processing unit, a second processing unit and a third processing unit;

a first processing unit, configured to receive a radio bearer configuration message sent by a CU of a base station; wherein the radio bearer configuration message contains one or more of the following information: CU allocates CU UE AP ID for UE, UE context information in S-DU, target cell identification, RB information to be configured, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel, uplink channel information and MBB switching indication;

the second processing unit is configured to send a radio bearer configuration response message to the CU; including in the radio bearer configuration response message one or more combinations of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by target DU for UE, and RB information configured for UE;

and the third processing unit is configured to receive data sent by the CU, receive an RRC connection setup complete message sent by the UE after the UE synchronizes to a target cell, and forward the RRC connection setup complete message to the CU through a user plane channel between the CU and the third processing unit.

The application also provides an access method of the UE, the UE is accessed through DU-1 and DU-2, the DU-1 and DU-2 correspond to the same CU, and the method comprises the following steps:

after the CU determines to switch a part of DRBs or all DRBs of the UE to the target DU, the CU sends a radio bearer configuration message to the target DU; wherein the radio bearer configuration message contains one or more of the following information: CU allocates CU UE AP ID, UE context information in source DU, target cell identification, RB information to be configured in target DU, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel, uplink channel information and MBB switching indication for UE by CU; wherein, corresponding to each DRB, the radio bearer configuration message contains uplink channel information allocated by a CU; the channel information comprises a transport layer address and a TEID;

the CU sends an RRC connection reconfiguration message to the source DU through the user plane channel or the control plane channel, and sends a combination of one or more of the following information to the source DU: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU-1 for UE, RRC connection reconfiguration, logic channel information for sending RRC message, information of RB to be switched away, and MBB switching indication;

the CU sends a UE context release message to the source DU.

The present application also provides a CU apparatus for UE access, the apparatus comprising: receiving unit, processing unit and transmitting unit, wherein:

the processing unit is configured to send a radio bearer configuration message to the destination DU through the sending unit after determining whether to switch a part of DRBs of the UE or all DRBs to the destination DU; wherein the radio bearer configuration message contains one or more of the following information: CU allocates CU UE AP ID, UE context information in source DU, target cell identification, RB information to be configured in target DU, configuration information of physical channel, configuration information of transmission channel, configuration information of logical channel, uplink channel information and MBB switching indication for UE by CU; wherein, corresponding to each DRB, the radio bearer configuration message contains uplink channel information allocated by a CU; the channel information comprises a transport layer address and a TEID;

the receiving unit is further configured to receive a radio bearer configuration response message sent by the destination DU; including in the radio bearer configuration response message one or more combinations of the following information: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by target DU for UE, and RB information configured for UE;

the sending unit is further configured to send an RRC connection reconfiguration message to the source DU through the user plane channel or the control plane channel, and send a combination of one or more of the following information to the source DU: CU UE AP ID distributed by CU for UE, DU UE AP ID distributed by DU-1 for UE, RRC connection reconfiguration, logic channel information for sending RRC message, information of RB to be switched away, and MBB switching indication;

the sending unit is further configured to send data to the destination DU, and after the UE synchronizes to the destination cell, the CU receives an RRC connection setup complete message sent by the destination DU through a user plane channel or a control plane channel; the RRC connection setup complete message is sent by the UE to the base station; and sends a UE context release message to the source DU.

The present application also provides a method performed by a central unit, CU, of a base station, gNB, the gNB comprising the CU and a plurality of distribution units, DU, the method comprising: identifying a target DU among the plurality of DUs based on a measurement report message associated with a terminal; sending a first message to the identified target DU for establishing a context associated with the terminal at the identified target DU, the first message including a first identity allocated by the CU for the terminal; receiving a second message from the identified target DU as a response to the first message, the second message including a first identity allocated by the CU to the terminal and a second identity allocated by the target DU to the terminal; and transmitting a third message to a source DU of the plurality of DUs, the third message including a radio resource control, RRC, reconfiguration message and information for stopping data transmission related to the terminal.

The present application further provides a centralized unit CU of a base station gNB, where the gNB includes the CU and a plurality of distribution units DU, and the CU includes: a transceiver; and a processor coupled with the transceiver and configured to control to: identifying a target DU among the plurality of DUs based on a measurement report message associated with a terminal, transmitting a first message to the identified target DU for establishing a context associated with the terminal at the identified target DU, the first message including a first identity assigned by the CU for the terminal, receiving a second message from the identified target DU as a response to the first message, the second message including the first identity assigned by the CU for the terminal and a second identity assigned by the target DU for the terminal, and transmitting a third message to a source DU among the plurality of DUs, the third message including a radio resource control, RRC, reconfiguration message and information for stopping data transmission related to the terminal.

The present application also provides a method performed by a source distribution unit, DU, of a base station, gNB, the gNB comprising a central unit, CU, and a plurality of DUs, the method comprising: receiving a measurement report message from a terminal; sending a first message including a measurement report message associated with the terminal to the CU of the gNB; receiving, from the CU of the gNB, a second message including a Radio Resource Control (RRC) reconfiguration message and information for stopping data transmission related to the terminal; and stopping data transmission related to the terminal based on the information.

The present application further provides a source distribution unit DU of a base station gNB, where the gNB includes a centralized unit CU and a plurality of DUs, and the source DU of the gNB includes: a transceiver; and a processor coupled with the transceiver and configured to control to: the method includes receiving a measurement report message from a terminal, sending a first message including the measurement report message associated with the terminal to the CU of the gNB, receiving a second message including a radio resource control, RRC, reconfiguration message and information for stopping data transmission related to the terminal from the CU of the gNB, and stopping data transmission related to the terminal based on the information.

The present application also provides a method performed by a target distribution unit, DU, of a base station, gNB, the gNB comprising a central unit, CU, and a plurality of DUs, the method comprising: receiving a first message from the CU for establishing a context associated with a terminal in a target DU, the first message comprising a first identity assigned by the CU for the terminal; configuring at least one of a Signaling Radio Bearer (SRB) or a Data Radio Bearer (DRB) for the terminal based on the first message; sending a second message to the CU as a response to the first message, the second message comprising a first identity assigned by the CU to the terminal and a second identity assigned by the target DU to the terminal; receiving a radio resource control, RRC, reconfiguration complete message from the terminal; and sending a third message including the RRC reconfiguration complete message to the CU.

The present application further provides a target distribution unit DU of a base station gNB, where the gNB includes a centralized unit CU and a plurality of DUs, and the target DU of the gNB includes: a transceiver; and a processor coupled with the transceiver and configured to control to: receiving a first message from the CU for establishing a context associated with a terminal in a target DU, the first message comprising a first identity assigned by the CU for the terminal; configuring at least one of a Signaling Radio Bearer (SRB) or a Data Radio Bearer (DRB) for the terminal based on the first message; sending a second message to the CU as a response to the first message, the second message comprising a first identity assigned by the CU to the terminal and a second identity assigned by the target DU to the terminal; receiving a radio resource control, RRC, reconfiguration complete message from the terminal; and sending a third message including the RRC reconfiguration complete message to the CU.

According to the technical scheme, the forward interface establishing method provided by the application can reduce the configuration of operators and ensure better intercommunication between the DU and the CU. In addition, the switching method and the access method of the UE on the F1 interface and the device thereof ensure that the DU and the CU can support interconnection and intercommunication among multi-vendor equipment.

Drawings

FIG. 1 is a system architecture diagram of a 5G network;

FIG. 2 is a schematic diagram of a method for establishing a forward interface according to the present invention;

FIG. 3 is a diagram illustrating a second method for establishing a forward interface according to the present invention;

FIG. 4 is a third schematic diagram illustrating a method for establishing a forward interface according to the present invention;

FIG. 5 is a diagram illustrating a method for accessing a UE according to the present invention;

FIG. 6 is a schematic diagram of a method for switching between different DUs of the same CU by the UE according to the present invention;

fig. 7 is a schematic diagram of a method for accessing by a UE through different DUs in the same CU according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by referring to the accompanying drawings and examples.

The application provides three establishing methods of a forward interface between a DU and a CU, and also provides a method for UE access and UE switching after the forward interface is established. The methods in the present application are described in detail below.

The first embodiment is as follows:

fig. 2 shows a method for establishing a forward interface according to the present invention. In this method, the F1 interface establishment procedure is initiated by the DU. The method can be used for the case that the O & M has interfaces with both the CU and the DU, or the case that the O & M has interfaces with only the DU. The method for establishing the forward interface comprises the processing of a DU side and the processing of a CU side, and for the convenience of description, the establishing method is introduced in a mode of interaction between the DU and the CU, and comprises the following steps:

in step 201, the DU sends F1 setup request message to the CU.

The operation and maintenance system (O & M) configures to the DU the transport layer address of the CU to which the DU is to be connected. The O & M also configures application layer information on the DU to the DU.

The F1 setup request message may contain one or more of the following information:

-DU identity.

-list of information of serving cells on the DU. The information of the serving cell includes: cell identity, frequency information of a cell, uplink transmission bandwidth, downlink transmission bandwidth information, physical cell identity, Tracking Area Identity (TAI) or Tracking Area Code (TAC), broadcasted Public Land Mobile Network (PLMN) identity list, Transmission Reception Point (TRP) information, Beam (Beam) information, physical channel information in the cell, transmission channel information in the cell, logical channel information in the cell, and/or cell access layer (AP) identity allocated by the DU for F1 interface. The cell identity may be a global cell identity or a unique cell identity on the DU or other cell identities received from the O & M. The cell AP id allocated by the DU is used to establish a cell signaling connection of the F1 interface, and is used to transmit cell-related information. The information of the serving cell also contains clock information, such as a System Frame Number (SFN).

Capability information of the DU. The DU capability information includes the buffering capability of the DU, the capacity information of the DU, the capability of the antenna, the power information, and/or the capability of the forward interface of the DU.

In step 202, the CU receives the F1 setup request message. The CU saves the received information and sends F1 setup response message to the DU.

If the CU receives capability information of the DUs, the CU uses said information to schedule the UE, e.g. to decide to select the DU serving the UE or to decide load balancing between different DUs.

Wherein the F1 setup response message may contain one or more of the following information in combination:

-a CU identification. The CU identification may be an identification of the gNB or an individual CU identification.

-list of PLMN identities supported by the CU.

-a cell configuration list. The cell configuration information in the cell configuration list includes: a cell identifier, configuration information of a common channel in the cell, system information in the cell, scheduling information sent by the system information, and/or a cell AP identifier allocated by the CU for an F1 interface. The cell identity may be a global cell identity or a unique cell identity on a DU or a unique cell identity on a CU. The common channel configuration information includes physical channel configuration information, transmission channel configuration information, and logical channel configuration information. The system information includes a Master Information Block (MIB) and a system information block. The CU determines scheduling information of system information based on the clock information of the cell received from the DU. The CU includes the clock information (e.g., SFN) of the cell received from the DU in the system information. The CU assigned cell AP identifies the cell signalling connection used to establish the F1 interface for the transmission of cell related information. Here, if the cell configuration list is included in the F1 setup response message, it means that cell setup is completed in the F1 setup procedure.

As described above, if the cell configuration list is included in the F1 setup response message, it means that the cell required on the DU is configured through the F1 setup procedure, and the cell configuration list includes the system information in the cell and the scheduling information for system information transmission, which is equivalent to transmitting the system information to be broadcasted in the cell to the DU, so that the DU can operate quickly. As another method of the present invention, the cell establishment procedure may be a separate procedure, in which case the cell configuration list is not included in the F1 establishment response message. Corresponding to the method, the method also comprises the following steps:

in step 203, the CU sends a cell setup request message to the DU.

The cell establishment request message contains cell information to be configured. The cell information to be configured is the same as the cell configuration information in step 202, and is not described herein again.

In step 204, the DU sends a cell establishment response message to the CU.

The cell establishment procedure may be used to configure one cell or to configure multiple cells. If a cell is configured, the messages in step 203 and step 204 are sent through a cell signaling connection, that is, the cell establishment request message and the cell establishment response message include the cell AP identity allocated by the DU and the cell AP identity allocated by the CU.

In the method, the system information to be broadcasted in the cell is sent to the DU through the cell establishing process, so that the DU can send the system information as soon as possible after the cell is configured. As another method of the present invention, the system information transmission may be a separate process. Corresponding to the method, the method also comprises the following steps:

in step 205, the CU sends a system information transfer message to the DU.

The system information transmission message comprises a cell identification, system information in the cell and scheduling information sent by the system information. The CU determines scheduling information of system information based on the clock information of the cell received from the DU. The CU includes the clock information of the cell, e.g., SFN, received from the DU in the system information.

The system information transmission procedure may be used to transmit system information of one cell or a plurality of cells. If the system information of a cell is sent, the message of step 205 is sent through a cell signaling connection, that is, the system information transmission message includes the cell AP identity allocated by the DU and the cell AP identity allocated by the CU, in this case, the system information transmission message may not need to include the cell identity.

This completes the description of the first method for establishing the F1 interface according to the present invention. By the method, the application layer information of the DU and the CU can be exchanged, the configuration cost of an operator is reduced, the public resources of the DU and the CU can be automatically and quickly configured after the DU is started, preparation is made for the access of a user, and the purpose of quick start is achieved.

Example two:

fig. 3 shows a second method for establishing a forward interface according to the present invention. In this method the F1 interface setup procedure is initiated by the CU. The method can be used in the case that the O & M has interfaces with both the CU and DU, or in the case that the O & M has interfaces with only the CU. The method for establishing the forward interface comprises the processing of a DU side and the processing of a CU side, and for the convenience of description, the establishing method is introduced in a mode of interaction between the DU and the CU, and comprises the following steps:

in step 301, the CU sends an F1 setup request message to the DU.

The O & M configures the transport layer address of the DU to which the CU is to connect to the CU. The O & M configures application layer information on the CU to the CU. If the O & M has an interface only with the CU, the O & M also configures the application layer information on each DU to which the CU is to connect to the CU.

-list of PLMN identities supported by the CU.

-list of information of serving cells on the DU. The information of the serving cell includes: the method comprises the following steps of cell identification, frequency information of a cell, uplink transmission bandwidth, downlink transmission bandwidth information, physical cell identification, tracking area identification TAI or tracking area code, broadcasted PLMN identification list, transmission receiving point TRP information, Beam information, physical channel information in the cell, transmission channel information in the cell, logical channel information in the cell and/or cell access layer AP identification which is distributed by the DU and used for an F1 interface. The cell identity may be a global cell identity or a unique cell identity on the DU or other cell identities received from the O & M. The cell AP id allocated by the DU is used to establish a cell signaling connection of the F1 interface, and is used to transmit cell-related information. The information of the serving cell also contains clock information, such as the system frame number SFN. It should be noted that the O & M only needs to include this information when it has an interface with the CU, and the O & M configures the configuration information of the DU to the CU and transmits the configuration information to the corresponding DU through the CU.

-a cell configuration list. The cell configuration information in the cell configuration list includes: a cell identifier, configuration information of a common channel in the cell, system information in the cell, scheduling information sent by the system information, and/or a cell AP identifier allocated by the CU for an F1 interface. The cell identity may be a global cell identity or a unique cell identity on a DU or a unique cell identity on a CU. The common channel configuration information includes physical channel configuration information, transmission channel configuration information, and logical channel configuration information. The system information comprises a master information block MIB and a system information block. The CU determines scheduling information of the system information based on the clock information of the DU cell. The CU includes the clock information (e.g., SFN) of the DU cell in the system information. The CU assigned cell AP identifies the cell signalling connection used to establish the F1 interface for the transmission of cell related information. Here, if the cell configuration list is included in the F1 setup request, it means that cell setup is completed in the F1 setup procedure.

In step 302, the DU receives the F1 setup request message. The DU stores the received information. If the DU receives the cell configuration information, the DU configures a corresponding cell. The DU sends F1a setup response message to the CU.

Wherein, the F1 setup response message may contain one or more of the following information in combination:

-DU identity.

-cell configuration information. The cell configuration information here is the actual configuration information of the DU to the cell, and may be different from the request of the CU.

The CU saves the received information. If the CU receives capability information of the DUs, the CU uses said information to schedule the UE, e.g. to decide to select the DU serving the UE or to decide load balancing between different DUs. The CU sends an F1 setup response message to the DU.

As described above, if the cell configuration list is included in the F1 setup request message, it is equivalent to that the cell required on the DU is configured through the F1 setup procedure, and the cell configuration list includes the system information in the cell and the scheduling information transmitted by the system information, which is equivalent to that the system information to be broadcasted in the cell is transmitted to the DU, so that the DU can operate quickly. As another method of the present invention, the cell establishment procedure may be a separate procedure, in which case the cell configuration list is not included in the F1 establishment request message. Corresponding to the method, the method also comprises the following steps:

in step 303, the CU sends a cell setup request message to the DU.

The cell establishment request message contains cell information to be configured. The cell information to be configured is the same as the cell configuration information in step 301, and is not described herein again.

In step 304, the DU sends a cell setup response message to the CU.

in step 305, the CU sends a system information transfer message to the DU.

The system information transmission message comprises a cell identification, system information in the cell and scheduling information sent by the system information. The CU determines scheduling information of the system information based on the clock information of the DU cell. The CU includes clock information of the DU cell, e.g., SFN, in the system information.

The cell establishment procedure may be used to configure one cell or to configure multiple cells. If a cell is configured, the messages of step 303 and step 304 are sent through a cell signaling connection, that is, the system information transmission message includes the cell AP identity allocated by the DU and the cell AP identity allocated by the CU, in this case, the system information transmission message may not need to include the cell identity.

The system information transmission procedure may be used to transmit system information of one cell or a plurality of cells. If the system information of a cell is sent, the message of step 305 is sent through a cell signaling connection, that is, the system information transmission message includes the cell AP id allocated by the DU and the cell AP id allocated by the CU, in this case, the system information transmission message may not need to include the cell id.

Thus, the description of the second interface establishing method F1 according to the present invention is completed. By the method, the application layer information of the DU and the CU can be exchanged, the configuration cost of an operator is reduced, and the method can work under the condition that the O & M only has an interface with the CU. And after the DU is started, public resources of the DU and the CU can be automatically and quickly configured, so that preparation is made for the access of a user, and the purpose of quick start is achieved.

Example three:

fig. 4 shows a third method for establishing a forward interface according to the present invention. In this method the F1 interface establishment procedure is triggered by the CU. The method can be used in the case that the O & M has interfaces with both the CU and DU, or in the case that the O & M has interfaces with only the CU. The method for establishing the forward interface comprises the processing of a DU side and the processing of a CU side, and for the convenience of description, the establishing method is introduced in a mode of interaction between the DU and the CU, and comprises the following steps:

in step 401, the CU sends F1 setup request message to the DU.

Wherein, the F1 setup requirement message may contain one or more of the following information in combination:

-list of PLMN identities supported by the CU.

In step 402, the DU sends F1a setup request message to the CU. The DU gets application layer information on the DU from the O & M configuration or from the CU.

-DU identity.

-list of information of serving cells on the DU. The information of the serving cell includes: the method comprises the following steps of cell identification, frequency information of a cell, uplink transmission bandwidth, downlink transmission bandwidth information, physical cell identification, tracking area identification TAI or tracking area code, broadcasted PLMN identification list, transmission receiving point TRP information, Beam information, physical channel information in the cell, transmission channel information in the cell, logical channel information in the cell and/or cell access layer AP identification which is distributed by the DU and used for an F1 interface. The cell identity may be a global cell identity or a unique cell identity on the DU or other cell identities received from the O & M. The cell AP id allocated by the DU is used to establish a cell signaling connection of the F1 interface, and is used to transmit cell-related information. The information of the serving cell also contains clock information, such as the system frame number SFN.

The application layer information of the DU is obtained from the CU in this way, that is, if the F1 in step 401 establishes that the demand message includes the information list of the serving cell on the DU, this step does not need to include the information list of the serving cell on the DU.

In step 403, the CU receives the F1 setup request message. The CU saves the received information. If the CU receives capability information of the DUs, the CU uses said information to schedule the UE, e.g. to decide to select the DU serving the UE or to decide load balancing between different DUs. The CU sends an F1 setup response message to the DU.

-list of PLMN identities supported by the CU.

-a cell configuration list. The cell configuration information in the cell configuration list includes: a cell identifier, configuration information of a common channel in the cell, system information in the cell, scheduling information sent by the system information, and/or a cell AP identifier allocated by the CU for an F1 interface. The cell identity may be a global cell identity or a unique cell identity on a DU or a unique cell identity on a CU. The common channel configuration information includes physical channel configuration information, transmission channel configuration information, and logical channel configuration information. The system information comprises a master information block MIB and a system information block. The CU determines scheduling information of the system information based on the clock information of the DU cell. The CU includes clock information of the DU cell, e.g., SFN, in the system information. The CU assigned cell AP identifies the cell signalling connection used to establish the F1 interface for the transmission of cell related information. Here, if the cell configuration list is included in the F1 setup response, it is equivalent to that the cell setup is completed in the F1 setup procedure.

As described above, if the cell configuration list is included in the F1 setup response message, it is equivalent to that the cell required on the DU is configured through the F1 setup procedure, and the cell configuration list includes the system information in the cell and the scheduling information transmitted by the system information, which is equivalent to that the system information to be broadcasted in the cell is transmitted to the DU, so that the DU can operate quickly. Alternatively, as another method of the present invention, the cell establishment procedure may be a separate procedure, in which case the cell configuration list is not included in the F1 establishment response message. The specific steps are the same as those described in 203 and 204, and are not described herein again.

In the method, the system information to be broadcasted in the cell is sent to the DU through the cell establishing process, so that the DU can send the system information as soon as possible after the cell is configured. As another method of the present invention, the system information transmission may be a separate process. Corresponding to this method, the specific steps are the same as those described in 205, and are not described herein again.

When the application layer information of the DU is updated, for example, the capability information or the clock information of the DU is updated, the DU sends a DU configuration update message to the CU to notify the CU of the updated application layer information. The CU saves the received information. Optionally, the CU may also send a DU configuration update response message to the DU. When the CU receives the update information of the DU and needs to update the system information, the CU sends a system information update message to the DU, wherein the message contains the updated system information and/or the scheduling information of the system information. The CU may also transmit updated system information and/or scheduling information of the system information to the DU through a DU configuration update response message.

When the application layer information of the CU is updated, for example, when the PLMN list information supported by the CU is updated, the CU sends a CU configuration update message to the DU, and notifies the DU of the updated application layer information. The DU stores the received information. Optionally, the DU may also send a CU configuration update response message to the CUs.

Example four:

the UE access method of the present invention is shown in fig. 5, and the method can be used in the scenarios of Attach (Attach), Packet Data Network (PDN) connection establishment, and the like.

The access network entity is the gbb for the UE and the core network (including AMF and UPF). If the gNB is further divided into CU and DU function entities, it is invisible to the UE and the core network. Thus, in describing the communication procedure with the UE, the RRC procedure between the UE and the gNB is described; in describing the communication procedure with the core network, a procedure between the gNB and the AMF or the UPF is described. If the gNB is divided into a CU and a DU function entity, the entity which actually receives the RRC message from the UE at the gNB side is the DU, and then the DU is sent to the CU; and the entity that first receives the NG message from the AMF on the side of the gNB is the CU. For simplicity of description, the interface procedure between the UE and the gNB is directly described as the interface procedure between the UE and the DU, and the procedure between the gNB and the AMF or the UPF is directly described as the procedure between the CU and the AMF or the UPF in the present invention. A detailed description of the steps not relevant to the present invention, such as the processes between the AMF and SMF and UPF, is omitted here. The method shown in fig. 5 comprises the following steps:

in step 501, the UE sends an RRC connection request message to the base station.

In step 502, the DU receives a message from the UE. The DU knows that the UE is in idle mode or inactive mode by receiving a message from the UE on the Common Control Channel (CCCH). The DU sends an initial UE message transfer message to the CU.

The initial UE messaging message is an F1 application layer AP message. The message may contain a combination of one or more of the following information elements:

DU UE AP ID assigned by DU to UE.

-cell identity. I.e. in which cell the DU receives the message from the UE. The cell id may be a global cell id or a unique cell id under DU or a unique cell id under CU. And if the cell identity is the only cell identity under the DU, the initial UE message transmission message also comprises the DU identity.

-Tracking Area Identity (TAI).

-RRC message received from UE.

The DU is a cell radio network temporary identity (C-RNTI) allocated for the UE.

RRC messages between DU and CU can be transmitted over the control plane (i.e. over F1AP messages), or: RRC messages on the signaling radio bearer SRB0 are transported over the control plane and RRC messages on the other SRBs are transported over the user plane, i.e. over the GPRS tunneling protocol (GTP-U) of the user plane.

Corresponding to the method that the RRC message on the SRB0 is transmitted through a control plane, the RRC messages on other SRBs are transmitted through a user plane, the RRC messages on other SRBs can be transmitted through the same user plane channel, or a user plane channel can be established corresponding to each SRB and transmitted through different channels. In the latter method, the allocated channel information described below corresponds to each SRB. The present embodiment provides three ways to establish the user plane channel for transmitting RRC messages between the DU and CU:

the first method is as follows: in step 502, the DU allocates downlink channel information, and sends the allocated downlink channel information to the CUs via an initial UE message transmission message. In step 503, the CU allocates uplink channel information, and sends the allocated uplink channel information to the DU through a radio bearer configuration message. The downlink channel information and the uplink channel information comprise a channel identification (TEID) and/or a transport layer address.

The second method comprises the following steps: in step 502, the DU allocates downlink channel information, and sends the allocated downlink channel information to the CUs via an initial UE message transmission message. In step 505, the CU allocates uplink channel information, and sends the allocated uplink channel information to the DU through a downlink RRC transmission message. The downlink channel information and the uplink channel information comprise a channel identification TEID and/or a transport layer address.

The third method comprises the following steps: in step 503, the CU allocates uplink channel information, and sends the allocated uplink channel information to the DU through a radio bearer configuration message. In step 504, the DU allocates downlink channel information, and sends the allocated downlink channel information to the CU through a radio bearer configuration response message. The downlink channel information and the uplink channel information comprise a channel identification TEID and/or a transport layer address.

In step 503, the CU receives the initial UE message transfer message from the DU. According to the RRC message contained in the message, the CU knows that the message is the RRC connection request message. The CU assigns the CU UE AP ID on the F1 interface to the UE. The CU sends a radio bearer configuration message to the DU, requests the DU to establish the UE context and configures the radio bearer for the UE, wherein the radio bearer is configured by the SRB. The radio bearer configuration message may include one or more of the following information elements:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-an identity of the cell where the UE is located. The cell identity is a global cell identity or a unique cell identity under DU or a unique cell identity under CU.

-RB information to be configured. The RBs included in the message may be Signaling Radio Bearers (SRBs) and/or Data Radio Bearers (DRBs). In this step, the RB to be configured is an SRB.

-configuration information of the physical channel.

-configuration information of the transmission channel.

-configuration information of logical channels.

-upstream channel information. Corresponding to the aforementioned first and third ways of establishing the user plane channel for transmitting RRC messages between the DU and the CU, the radio bearer configuration message includes uplink channel information allocated by the CU. The path information is transmitted for RRC messages on all other SRBs except SRB 0. Or there is allocated channel information for each SRB.

The radio bearer configuration request message may also be a UE context setup request or other message name without affecting the main content of the present invention.

In step 504, the DU configures resources. The DU sends a radio bearer configuration response message to the CU. The radio bearer configuration response message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-RB information configured for the UE. The RB information is configuration information of the SRB. Corresponding to the aforementioned third user plane channel mode for establishing RRC message transmission between the DU and the CU, the radio bearer configuration response message includes downlink channel information allocated by the DU.

The DU is the C-RNTI allocated for the UE.

In the method of the present invention, the DU may send the C-RNTI allocated by the DU to the UE to the CU through this step or step 502. And when the CU receives the C-RNTI allocated by the DU to the UE, the CU stores the C-RNTI. Therefore, the CU knows the C-RNTI value distributed by the DU to the UE in the cell, and when the CU needs to distribute the C-RNTI value to the UE in the switching process, the CU selects the C-RNTI value which is not distributed in the cell to distribute to the UE.

The radio bearer configuration response message may also be a UE context setup response or other message name without affecting the main content of the present invention.

In step 505, the CU sends a downlink RRC transmission message to the DU. The downlink RRC transmission message comprises one or more of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-an RRC message. In this embodiment, the RRC message is an RRC connection setup message. The CU can send the C-RNTI allocated for the UE to the UE through an RRC message.

-transmitting logical channel information of the RRC message.

-upstream channel information. Corresponding to the second user plane channel mode for establishing the RRC message transmitted between the DU and the CU, the downlink RRC transmission message includes uplink channel information allocated by the CU. The path information is transmitted for RRC messages on all other SRBs except SRB 0. Or there is allocated channel information for each SRB.

The CU may also send an RRC connection setup message to the DU through the message of step 503. Step 505 may not be performed in response to this method.

In step 506, the DU sends the received RRC message to the UE.

In step 507, the UE sends an RRC connection setup complete to the base station.

In step 508, the DU sends the received RRC message to the CU via the control plane or the user plane. From the messages received on the allocated DCCH resources, the DU knows which UE the received RRC message is for.

The DU sends an uplink RRC transmission message to the CU in a manner corresponding to the sending of the received RRC message to the CU through the control plane. The uplink RRC transmission message may include one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-an RRC message. In this embodiment, the RRC message is an RRC connection setup complete message.

And correspondingly, in a mode of sending RRC messages on SRBs except the SRB0 to the CU through the user plane, the DU sends uplink RRC messages to the CU through the GTP-U.

Corresponding to the way that the RRC messages on other SRBs except for SRB0 are transmitted through a user plane channel, the user plane header may contain information of the SRB, such as SRB1 or SRB 2. Or the CU may indirectly know the SRB information of the received RRC message by parsing the RRC message.

The RRC messages on the SRBs other than SRB0 are each in a manner such that each SRB has a corresponding user plane channel, and the DU selects which of the established user plane channels to transmit to the CU based on the SRB on which the RRC message was received.

In step 509, the CU sends an initial UE message to the AMF.

If the AMF only needs to send NAS information to the UE and does not need to establish a session, the AMF sends a downlink NAS transmission information to the base station; if the session needs to be established, the AMF transmits an initial context setup request message of step 510 to the base station.

In step 510, the AMF sends an initial UE context setup request message to the CU.

If the CU receives the downlink NAS transport message from the AMF, the CU directly proceeds to the subsequent step without performing the RB reconfiguration procedure of step 511 to step 516.

The CU sends RRC message downlink NAS transmission messages to the DU through the control plane or the user plane.

Correspondingly, in a mode of sending an RRC message to the DU through the control plane, the CU sends a downlink RRC transmission message to the DU. The downlink RRC transmission message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-an RRC message. In this embodiment, the RRC message is a downlink NAS transport message.

And correspondingly, the CU sends the downlink NAS transmission message to the DU through the GTP-U in a mode of sending RRC messages on SRBs except the SRB0 through the user plane.

Corresponding to the way that the RRC messages on other SRBs except for SRB0 are transmitted through a user plane channel, the user plane header may contain information of the SRB, such as SRB1 or SRB 2. The user plane header may also contain information on which logical information the RRC message needs to be transmitted.

And each SRB corresponds to the RRC messages on other SRBs except the SRB0 in a mode that each SRB has a corresponding user plane channel, the CU sends the RRC message to the DU on the corresponding channel, and the DU learns which SRB the RRC message is sent to the UE on according to the channel receiving the information.

In step 511, the CU sends a radio bearer reconfiguration request message to the DU. The radio bearer reconfiguration request message may contain a combination of one or more of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-RB information to be added. The RB information to be added includes an RB identity, configuration information of a physical channel of the RB, configuration information of a transport channel of the RB, configuration information of a logical channel of the RB, QoS Flow (Flow) information mapped on the RB, and/or uplink channel information of the RB. And the QoS Flow information mapped on the RB comprises a Flow identifier and Qos information corresponding to the Flow. The uplink channel information includes a transport layer address and an uplink TEID.

-RB information to reconfigure. The RB information to be reconfigured includes an RB identity, reconfiguration information of a physical channel of the RB, reconfiguration information of a transport channel of the RB, reconfiguration information of a logical channel of the RB, QoS Flow information to be added to the RB, QoS Flow information to be deleted from the RB, and/or QoS Flow information to be transmitted to the RB. And the QoS Flow information to be added on the RB comprises a Qos Flow identifier and Qos Flow Qos information. And the QoS Flow information to be reconfigured on the RB comprises a Qos Flow identifier and a Qos parameter to be reconfigured. And the QoS Flow information to be deleted on the RB comprises a Qos Flow identifier.

-RB information to be deleted. The RB information to be deleted includes an RB identification.

User plane data transmission between the DU and CU may share one GTP-U channel for multiple RBs, or may use one GTP-U channel for each RB.

In step 512, the DU allocates resources. The DU sends a radio bearer reconfiguration response message to the CU. The radio bearer reconfiguration response message may contain a combination of one or more of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-configuration information of RBs. The configuration information of the RB includes RB identification and downlink channel information distributed by the DU. The downlink channel information includes a transport layer address and an uplink TEID.

In step 513, the CU sends an RRC message RRC connection reconfiguration to the DU through the control plane or the user plane.

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-an RRC message. In this embodiment, the RRC message is RRC connection reconfiguration.

Correspondingly, in a mode of sending RRC messages on SRBs except the SRB0 through the user plane, the CU sends RRC connection reconfiguration to the DU through the GTP-U.

And each SRB corresponds to the RRC messages on other SRBs except the SRB0 in a mode that each SRB has a user plane channel, the CU sends the RRC message to the DU on the corresponding channel, and the DU learns which SRB the RRC message is sent to the UE on according to the channel receiving the information.

In step 5014, the DU sends the RRC message received from the CU to the UE.

In step 5015, the UE sends an RRC connection reconfiguration complete message to the base station.

In step 5016, the DU sends the received RRC message to the CU via the control plane or the user plane. From the messages received on the allocated DCCH resources, the DU knows which UE the RRC message is for.

The DU sends an uplink RRC transmission message to the CU corresponding to the way the control plane sends the received RRC message to the CU. The uplink RRC transmission message may include one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

DU UE AP ID assigned by DU to UE.

-an RRC message. In this embodiment, the RRC message is an RRC connection setup reconfiguration complete message.

The DU selects which established user plane channel to transmit to the CU based on the SRBs that received the RRC message in a manner that each SRB has a user plane channel for the RRC messages on other SRBs except SRB 0.

Thus, the description of the UE access method of the present invention is completed. By the method, the problem of UE access when the gNB is divided into the DU and the CU can be solved, the method can be used in the scenes of Attach, PDU establishment and the like, and the DU and the CU can be guaranteed to support interconnection and intercommunication of multi-manufacturer equipment.

Example five:

the method for switching between different DUs of the same CU by the UE (i.e. the source DU and the destination DU of the switch correspond to the same CU) is shown in FIG. 6. Detailed descriptions of steps not relevant to the present invention, such as the processes between the AMF and SMF and UPF, are omitted here. The method comprises the following steps:

step 601, the UE sends a measurement report message to the base station. After receiving the RRC message from the UE, the DU sends the RRC message to the CU through the control plane or the user plane. The method of sending via the control plane and via the user plane is the same as that described in step 508 and step 516, and is not described herein again. The DU of this step is a source DU (S-DU).

In step 602, the CU decides to initiate a handover to the UE. The destination cell for handover is in the other DU. The CU decides whether to perform the normal handover or the handover before disconnection (MBB). The CU sends a radio bearer configuration message to a destination DU (T-DU), requests the T-DU to establish a UE context and configures a radio bearer for the UE, wherein the radio bearer comprises the configuration of the SRB and the DRB.

The radio bearer configuration message may contain one or more of the following information elements:

CU UE AP ID allocated by CU for UE.

-context information of the UE in the S-DU. The context information of the UE in the S-DU includes the cell identity of the UE in the source cell, the RB configuration information of the UE in the source cell and/or the capability information of the UE, etc.

-destination cell identity. The target cell identification is global cell identification of the target cell or unique cell identification under DU or unique cell identification under CU.

-RB information to be configured in the T-DU. The RBs included in the message may be SRBs and/or DRBs. In this step, RBs to be configured are SRB and DRB information.

-configuration information of the physical channel.

-configuration information of the transmission channel

-configuration information of logical channels.

-upstream channel information. And corresponding to each DRB, the message contains the uplink channel information allocated by the CU. Corresponding to the method that other RRC messages except the SRB0 are transmitted through the user plane, the radio bearer configuration message contains the uplink channel information distributed by the CU for the SRB, and the communication information can be a channel which corresponds to each SRB or is common to the transmission of the RRC messages on all the SRBs except the SRB 0. The channel information includes a transport layer address and a TEID.

-indication of MBB handover. This information is included when the CU decides to perform the MBB handover.

The radio bearer configuration message may also be a UE context setup request or other message name without affecting the main content of the present invention.

The invention provides two methods for distributing C-RNTI for UE in the switching process:

the method comprises the following steps: C-RNTI of a target cell is distributed to the UE by the CU;

the second method comprises the following steps: and C-RNTI of a target cell is distributed to the UE by the target DU.

And correspondingly, in the first method for allocating the C-RNTI to the UE, the CU allocates the C-RNTI in the target cell to the UE. The CU sends the allocated C-RNTI to the destination DU through a radio bearer configuration message. The CU needs to ensure the uniqueness of the C-RNTI in the cell when allocating the C-RNTI to the UE. Since the DU allocates the C-RNTI for the UE in the initial access process of the UE, the DU transmits the C-RNTI allocated for the UE to the CU, so that the CU can transmit the C-RNTI allocated for the UE to the UE through an RRC message. And when the CU receives the C-RNTI distributed by the DU to the UE, the CU stores the C-RNTI, so that the CU can acquire the C-RNTI distributed by the DU to the UE in the cell, and when the CU needs to distribute the C-RNTI to the UE in the switching process, the CU selects the C-RNTI value which is not distributed in the cell to distribute to the UE.

Step 603, the T-DU configures the resource. The T-DU sends a radio bearer configuration response message to the CUs. The radio bearer configuration response message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

-DU UE AP ID allocated by the T-DU to the UE.

-RB information configured for the UE. The RB information includes configuration information of SRBs and DRBs. Corresponding to each DRB, the message contains the downlink channel information distributed by the T-DU. The method for transmitting other RRC messages except the SRB0 through the user plane comprises the downlink channel information distributed by the T-DU for the SRB, and the communication information can be the channel which is corresponding to each SRB or is common to the RRC message transmission on all the SRBs except the SRB 0. The channel information includes a transport layer address and a TEID.

And correspondingly, in the second method for allocating the C-RNTI to the UE, the target DU allocates the C-RNTI in the target cell to the UE. And the destination DU sends the allocated C-RNTI to the CU through a radio bearer configuration response message. When the target DU allocates the C-RNTI to the UE, the uniqueness of the C-RNTI in the cell needs to be ensured.

Corresponding to the first method for allocating C-RNTI to UE, the target DU stores the C-RNTI contained in the received radio bearer configuration message. The value of the C-RNTI is not used when the target DU allocates the C-RNTI for the UE initially accessed next time. If the C-RNTI included in the radio bearer configuration message received by the target DU is already allocated to another UE, the target DU has two processing modes:

the first method is as follows: the destination DU sends a radio bearer configuration failure message to the CU. The message may contain the reason for the failure: invalid C-RNTI. The CU ends the process of switching the UE to the T-DU.

The second method comprises the following steps: the destination DU allocates another unused C-RNTI to the UE and sends the new C-RNTI to the CU via the radio bearer configuration response message. And after the CU receives the new C-RNTI from the DU, the C-RNTI allocated by the UE is modified.

In step 604, the CU sends an RRC connection reconfiguration message to the S-DU through the control plane or the user plane. And the CU includes the C-RNTI allocated to the UE in the target cell in the RRC connection reconfiguration message, wherein the C-RNTI is allocated to the CU or the target DU. And correspondingly, the CU sends a downlink RRC transmission message to the S-DU in a control plane transmission mode. The downlink RRC transmission message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

The S-DU assigns a DU UE AP ID for the UE.

-transmitting logical channel information of the RRC message.

-information of handover between different DUs. If the S-DU receives the information of switching between different DUs, the S-DU stops sending data to the UE after sending the received RRC message to the UE. Uplink data from the UE is no longer received.

-indication of MBB handover. If the S-DU receives the MBB handover indication information, it may continue to send data to the UE and receive uplink data from the UE after sending the received RRC message to the UE. And the S-DU stops transmitting the downlink data to the UE and/or stops receiving the data from the UE after receiving the data transmission stop instruction from the CU. Or the S-DU decides when to stop sending data to the UE, e.g. when the S-DU stops sending data to the UE after it no longer receives the uplink acknowledgement from the UE.

In response to the way RRC connection reconfiguration messages are sent to the S-DU over the user plane, the CU sends the following information to the S-DU over a separate F1AP message or includes the following information in the data header:

Correspondingly to the mode of sending the RRC connection reconfiguration message to the S-DU through the user plane, the data packet header also comprises a CU UE AP ID distributed by the CU for the UE, a DU UE AP ID distributed by the S-DU for the UE and/or logic channel information for sending the RRC message.

In step 605, the DU sends the received RRC message to the UE.

And when the CU decides that the S-DU stops sending the downlink data to the UE or stops communication with the UE, the CU sends a data stop indication message to the S-DU. And after receiving the corresponding message from the CU, the S-DU stops the communication with the UE.

The CU may start sending data to the T-DU, the CU sending data that the UE did not acknowledge and received from the UPF to the T-DU. The data is a PDCP PDU.

There are two methods of data transmission:

in the first method, the CU directly sends data that the UE does not acknowledge and that is received from the UPF to the T-DU. The data is a PDCP PDU. No data forwarding between S-DU and T-DU is required.

In the second method, the CU directly sends the data which is not confirmed by the UE and is received from the UPF to the T-DU. The data is a PDCP PDU. In order to avoid that some RLC PDUs have been successfully transmitted from the source DU to the UE and repeatedly transmitted in the destination DU, the S-DU sends the RLC context of the source side to the T-DU. Corresponding to the PDCP PDU successfully sent by the part, the T-DU only sends the RLC PDU which is not received by the UE to the UE, and does not need to send the whole PDCP PDU to the UE, so that the repeated sending of data is avoided. Corresponding to this method, steps 605a and 605b are also performed. This method is applicable to the case where the T-DU and the S-DU have the same RB configuration. Optionally, the S-DU may also forward RLC PDUs that the UE does not acknowledge to the T-DU.

In step 605a, the S-DU sends an RLC context transfer message to the CU. The RLC context transfer message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

The S-DU assigns a DU UE AP ID for the UE.

RLC transmission status. The RLC transmission status contains the SN of the last successfully transmitted GTP-U packet. Unsuccessfully transmitted GTP-U packet SN and/or unsuccessfully transmitted RLC SN.

In step 605b, the CU sends an RLC context transfer two message to the T-DU. The RLC context transfer two message may contain a combination of one or more of the following information:

CU UE AP ID allocated by CU for UE.

-DU UE AP ID allocated by the T-DU to the UE.

RLC transmission status. The RLC transmission status contains the SN of the last successfully transmitted GTP-U packet. Unsuccessfully transmitted GTP-U packet SN and unsuccessfully transmitted RLC SN.

-PDCP transmit receive status. The PDCP sending state comprises the SN of the last successfully sent GTP-U data packet, the receiving state of unsuccessfully sent GTP-U data packet SN and/or uplink PDCP. The DU determines which PDCP data packets UE receive the complete data packets and which PDCP data packets UE do not receive the complete data packets according to the feedback of the RLC layer UE, thereby determining the PDCP sending and receiving state.

The RLC context transfer may also be called PDCP context transfer or by other names without affecting the main content of the invention.

In the method of the present invention, only step 605a may be executed to notify the transmitting/receiving status of the PDCP packet to the CU, so that the CU knows which PDCP packets to transmit to the T-DU.

Step 605a and step 605b are not optional steps of the present invention.

Step 606, the UE synchronizes to the destination cell.

In step 607, the UE sends an RRC connection setup complete to the base station. The T-DU sends the received RRC message to the CUs via the control plane or the user plane. The specific method of sending the DU to the CU is the same as in step 5016, and is not described here.

In step 608, the CU sends a UE context release message to the S-DU. The message contains CU UE AP ID distributed by CU for UE, and DU UE AP ID distributed by S-DU for UE.

Thus, the description of the method for switching the UE between different DUs according to the present invention is completed. By the method, the problem of UE switching when the gNB is divided into the DU and the CU can be solved, data loss is avoided, and the DU and the CU are ensured to support interconnection and intercommunication of multi-vendor equipment.

Example six:

the method for accessing UE through different DUs of the same CU (i.e. accessing UE through DU-1 and DU-2, and accessing DU-1 and DU-2 corresponding to the same CU) is shown in FIG. 7. A detailed description of the steps not relevant to the present invention, such as the processes between the AMF and SMF and UPF, is omitted here. The method comprises the following steps:

in step 701, the UE sends a measurement report message to the base station. After receiving the RRC message from the UE, the DU sends the received RRC message to the CU through the control plane or the user plane. The method of sending via the control plane and via the user plane is the same as that described in step 508 and step 516, and is not described herein again. The DU of this step is the DU currently serving the UE (DU-1).

In step 702, the CU decides to switch a part of the bearers of the UE to the cell of DU-2 based on the measurement report of the UE. The CU decides whether to perform normal switching or MBB switching. The CU sends a radio bearer configuration message to DU-2, requests DU-2 to establish UE context and configures radio bearer for the UE. The CU decides whether to switch part of the DRBs or all DRBs to DU-2. If SRB is also handed over to DU-2, it means that it is a handover procedure from DU-1 to DU-2, and DRB is established in DU-1, which is equivalent to the combination of the handover procedure in fig. 5 and the procedure of handing over part or all of DRB to DU-2 in this embodiment, and will not be described in detail here. The radio bearer configuration message may contain one or more of the following information elements:

CU UE AP ID allocated by CU for UE.

Context information of the UE in DU-1. The context information of the UE comprises cell identification of the UE in a DU-1 cell, RB configuration information of the UE in the DU-1 cell and/or capability information of the UE and the like.

-destination cell identity. The cell identity is a global cell identity or a unique cell identity under DU or a unique cell identity under CU.

RB information to be configured in DU-2.

-configuration information of the physical channel.

-configuration information of the transmission channel

-configuration information of logical channels.

-upstream channel information. And corresponding to each DRB, the message contains the uplink channel information allocated by the CU. The channel information includes a transport layer address and a TEID.

-indication of MBB handover.

There are two methods for allocating the C-RNTI to the UE:

the method comprises the following steps: C-RNTI distributed in a DU-2 cell by the CU for the UE;

the second method comprises the following steps: and C-RNTI of the DU-2 cell is allocated to the UE by the DU-2.

And correspondingly, in the first method for allocating C-RNTI to the UE, the CU allocates C-RNTI in the DU-2 cell to the UE. The CU sends the allocated C-RNTI to the DU-2 via the radio bearer configuration message. The CU needs to ensure the uniqueness of the C-RNTI in the cell when allocating the C-RNTI to the UE. Since the DU allocates the C-RNTI for the UE in the initial access process of the UE, the DU transmits the C-RNTI allocated for the UE to the CU, so that the CU can transmit the C-RNTI allocated for the UE to the UE through an RRC message. And when the CU receives the C-RNTI distributed by the DU to the UE, the CU stores the C-RNTI, so that the CU knows the C-RNTI distributed by the DU to the UE in the cell, and when the CU needs to distribute the C-RNTI to the UE, the CU selects the C-RNTI value which is not distributed in the cell to distribute to the UE.

Step 703, DU-2 configures resources. DU-2 sends a radio bearer configuration response message to the CU. The radio bearer configuration response message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

DU-2 allocated DU UE AP ID for UE.

-RB information configured for the UE. Corresponding to each RB, the radio bearer configuration response message contains downlink channel information distributed by the DU-2. The channel information includes a transport layer address and a TEID.

And correspondingly, in the second method for allocating the C-RNTI for the UE, the DU-2 allocates the C-RNTI of the UE in the DU-2 cell. The DU-2 transmits the allocated C-RNTI to the CU through a radio bearer configuration response message. DU-2 needs to guarantee the uniqueness of the C-RNTI in the cell when the C-RNTI is allocated to the UE.

Corresponding to the first method for allocating C-RNTI to UE, DU-2 stores the C-RNTI contained in the received radio bearer configuration message. The next time DU-2 allocates C-RNTI to the UE for initial access, the value of the C-RNTI is not used. If the C-RNTI included in the radio bearer configuration message received by the DU-2 is already allocated to another UE, the DU-2 has two processing modes:

the first method is as follows: DU-2 sends a radio bearer configuration failure message to the CU. The message may contain the reason for the failure: invalid C-RNTI. The CU ends the process of configuring the UE to DU-2.

The second method comprises the following steps: DU-2 allocates another unused C-RNTI to the UE and sends the new C-RNTI to the CU via a radio bearer configuration response message. And after receiving the new C-RNTI from the DU-2, the CU modifies the C-RNTI allocated by the UE.

In step 704, the CU sends an RRC connection reconfiguration message to DU-1 via the control plane or the user plane. The CU includes the C-RNTI in the DU-2 cell allocated for the UE in the RRC connection reconfiguration message. The C-RNTI is allocated by the CU or the DU-2. Correspondingly, the CU sends a downlink RRC transmission message to the DU-1 in a control plane transmission mode. The downlink RRC transmission message may contain one or a combination of the following information:

CU UE AP ID allocated by CU for UE.

DU-1 allocated DU UE AP ID for UE.

-transmitting logical channel information of the RRC message.

-information of RBs to switch away. The RB information to be switched away includes an RB identity, an identity of a destination DU, and/or an identity of a destination cell. For the RB to be switched, DU-1 stops sending data to the UE after sending the received RRC message to the UE, and does not receive uplink data from the UE. The CU may also send RB information to be switched away to DU-1 through a separate message. In this way, the message for CU to notify the DU of the RB information to switch away and the message of this step may be after or before this step.

-indication of MBB handover. If DU-1 receives the MBB handover indication information, after sending the received RRC message to the UE, it may continue to send data to the UE on the RB to be handed over and receive uplink data from the UE. The DU-1 stops transmitting downlink data to the UE and/or stops receiving data from the UE in the corresponding RB after receiving the data transmission stop instruction from the CU. Or DU-1 decides when to stop sending data to the UE, e.g. when DU-1 no longer receives the uplink acknowledgement from the UE.

In step 705, DU-1 sends the received RRC message to the UE.

And when the CU decides that the DU-1 stops sending the downlink data to the UE or stopping communication with the UE on the RB to be switched away, the CU sends a data stop indication message to the DU-1. Upon receipt of the corresponding message from the CU, DU-1 stops communication with the UE on the RB to be switched away.

The CU may start sending data to DU-2 on the RB to be switched to DU-2, and the CU sends data to DU-2 that the UE did not acknowledge and that was received from the UPF. The data is a PDCP PDU.

For the RB to be switched, there are two methods of data transmission:

in the first method, CU directly sends data that UE does not acknowledge and received from UPF to DU-2. The data is a PDCP PDU. No data forwarding between DU-1 and DU-2 is required.

In the second method, the CU directly sends the data that the UE did not acknowledge and that is received from the UPF to the DU-2. The data is a PDCP PDU. To avoid that some RLC PDUs have been successfully transmitted from DU-1 to the UE and repeatedly transmitted in DU-2, DU-1 sends the source side RLC context to DU-2. Corresponding to the PDCP PDU successfully sent by the part, the DU-2 only sends the RLC PDU which is not received by the UE to the UE, and does not need to send the whole PDCP PDU to the UE, so that the repeated sending of data is avoided. Corresponding to this method, it is also necessary to perform steps similar to

steps

605a and 605b, and DU-1 sends RLC context to DU-2 through the CU, which is different from

steps

605a and 605b in that the RLC context is only for the RB to be switched, and S-DU is DU-1 and T-DU is DU-2, and the rest are the same and will not be described herein again. This method is applicable to the case where the DU-1 and DU-2RB configurations are the same. Optionally, DU-1 may also forward RLC PDUs that the UE does not acknowledge to DU-2. Step 605a and step 605b are not optional steps of the present invention.

In step 706, the UE synchronizes to the destination cell.

In step 707, the UE sends an RRC connection setup complete to the base station. The DU-1 sends the received RRC message to the CUs through the control plane or the user plane. The specific method of sending DU-1 to the CU is the same as in step 5016 and will not be described herein.

In step 708, the CU sends a radio bearer configuration completion indication message to DU-2, and sends the RB configuration information received by the CU from the UE to DU-2. The message may contain only the configuration difference (delta configuration), i.e. the configuration of DU-2 to the UE, and the UE is not actually different according to the requirements of the network. The message may contain the complete configuration of the UE.

In step 709, the CU sends a radio bearer reconfiguration or RB release message to DU-1. The message contains CU UE AP ID distributed by CU for UE, and DU-1 is DU UE AP ID distributed by UE. The message contains RB information to be released or RB information for successful handover to DU-2. The RB information includes an RB identity.

In step 710, DU-1 sends a radio bearer reconfiguration response or RB release response message to the CU.

Thus, the description of the method for accessing the UE through different DUs in the same CU according to the present invention is completed. By the method, the problem that the UE is accessed through different DUs when the gNB is divided into the DUs and the CUs can be solved, the throughput of the UE is improved, the loss of data of switching load is avoided, and the DU and the CU are ensured to support the interconnection and intercommunication of multi-manufacturer equipment.

The forward interface establishing method, the UE accessing method and the switching method can solve the communication problem when the gNB is divided into the DU and the CU, reduce the configuration cost of an operator, improve the throughput of the UE, avoid data loss and ensure that the DU and the CU support interconnection and intercommunication of multi-manufacturer equipment.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method performed by a central unit, CU, of a base station, the base station comprising the CU and a plurality of distribution units, DU, the method comprising:

identifying a target DU among the plurality of DUs based on a measurement report message associated with a terminal;

sending a first message to the identified target DU for establishing a context associated with the terminal at the identified target DU, the first message including a first identity allocated by the CU for the terminal;

receiving a second message from the identified target DU as a response to the first message, the second message including a first identity allocated by the CU to the terminal and a second identity allocated by the target DU to the terminal; and

transmitting a third message to a source DU of the plurality of DUs, the third message including a Radio Resource Control (RRC) reconfiguration message and information for stopping data transmission related to the terminal.

2. The method of claim 1, further comprising:

receiving a fourth message from the identified target DU, the fourth message comprising an RRC reconfiguration complete message; and

sending a fifth message to the source DU, the fifth message being used for releasing the context associated with the terminal in the source DU.

3. The method of claim 2, further comprising:

receiving, from the source DU, a sixth message associated with a data transfer status based on the third message, the sixth message including at least one of: first information on sequence numbers of successfully transmitted data and second information on sequence numbers of unsuccessfully transmitted data.

4. The method of claim 3, wherein data to be transmitted to the target DU is identified based on the sixth message.

5. The method of claim 4, wherein the CU has Packet Data Convergence Protocol (PDCP) and RRC functions, and

wherein the source DU or the target DU has a physical layer function, a medium access control MAC function, and a radio link control RLC function.

6. The method of claim 1, wherein the first message further comprises at least one of: information associated with a signaling radio bearer SRB to be configured by the target DU or information associated with a data radio bearer DRB to be configured by the target DU, and

wherein the second message further comprises at least one of: information associated with an SRB to be configured by the target DU, or information associated with a DRB to be configured by the target DU.

7. The method of claim 1, wherein the measurement report message is received from the source DU.

8. The method of claim 1, wherein the second message further includes a cell radio network temporary identity (C-RNTI) allocated by the target DU to the terminal.

9. The method of claim 1, wherein the first message further comprises terminal wireless capability information.

10. A central unit, CU, of a base station, the base station comprising the CU and a plurality of distribution units, DU, the CU comprising:

a transceiver; and

a processor coupled with the transceiver and configured to control to:

identifying a target DU among the plurality of DUs based on a measurement report message associated with the terminal,

sending a first message to the identified target DU for establishing a context associated with the terminal at the identified target DU, the first message including a first identity allocated by the CU for the terminal,

receiving a second message from the identified target DU as a response to the first message, the second message including a first identity allocated by the CU to the terminal and a second identity allocated by the target DU to the terminal, and

11. The CU of claim 10, wherein the processor is further configured to control to:

12. The CU of claim 11, wherein the processor is further configured to control to:

13. The CU of claim 12, wherein the data to be sent to the target DU is identified based on the sixth message.

14. The CU of claim 13, wherein the CU has a packet data convergence protocol, PDCP, function and an RRC function, and

15. The CU of claim 10, wherein the first message further comprises at least one of: information associated with a signaling radio bearer SRB to be configured by the target DU or information associated with a data radio bearer DRB to be configured by the target DU, and

16. The CU of claim 10, wherein the measurement report message is received from the source DU.

17. The CU of claim 10, wherein the second message further comprises a cell radio network temporary identity, C-RNTI, assigned by the target DU for the terminal.

18. The CU of claim 10, wherein the first message further comprises terminal wireless capability information.

19. A method performed by a source distribution unit, DU, of a base station comprising a concentration unit, CU, and a plurality of DUs, the method comprising:

receiving a measurement report message from a terminal;

sending a first message including a measurement report message associated with the terminal to the CU of the base station;

receiving, from the CU of the base station, a second message including a Radio Resource Control (RRC) reconfiguration message and information for stopping data transmission related to the terminal; and

stopping data transmission related to the terminal based on the information,

the method further comprises the following steps:

sending, based on the second message, a third message associated with a data delivery status to the CU of the base station, the third message comprising at least one of: first information on sequence numbers of successfully transmitted data and second information on sequence numbers of unsuccessfully transmitted data.

20. The method of claim 19, further comprising:

receiving a fourth message from the CU of the base station for releasing a context associated with the terminal at the source DU of the base station, an

Releasing the context associated with the terminal at the source DU of the base station based on the fourth message.

21. The method of claim 19, wherein the CU has a packet data convergence protocol PDCP function and an RRC function, and

wherein the source DU has a physical layer function, a medium access control MAC function and a radio link control RLC function.

22. A source distribution unit, DU, of a base station, the base station comprising a concentration unit, CU, and a plurality of DUs, the source DU of the base station comprising:

a transceiver; and

a processor coupled with the transceiver and configured to control to:

a measurement report message is received from the terminal,

sending a first message including a measurement report message associated with the terminal to the CU of the base station,

receiving a second message including a Radio Resource Control (RRC) reconfiguration message and information for stopping data transmission related to the terminal from the CU of the base station, and

stopping data transmission related to the terminal based on the information,

wherein the processor is further configured to control to: sending, based on the second message, a third message associated with a data delivery status to the CU of the base station, the third message comprising at least one of: first information on sequence numbers of successfully transmitted data and second information on sequence numbers of unsuccessfully transmitted data.

23. The source DU of claim 22, wherein the processor is further configured to control to:

24. The source DU of claim 22, wherein the CUs have packet data convergence protocol PDCP and RRC functions, and

25. A method performed by a target distribution unit, DU, of a base station, the base station comprising a concentration unit, CU, and a plurality of DUs, the method comprising:

receiving a first message from the CU for establishing a context associated with a terminal in a target DU, the first message comprising a first identity assigned by the CU for the terminal;

configuring at least one of a Signaling Radio Bearer (SRB) or a Data Radio Bearer (DRB) for the terminal based on the first message;

sending a second message to the CU as a response to the first message, the second message comprising a first identity assigned by the CU to the terminal and a second identity assigned by the target DU to the terminal;

receiving a radio resource control, RRC, reconfiguration complete message from the terminal; and

sending a third message to the CU including the RRC reconfiguration complete message.

26. The method of claim 25, wherein the first message further comprises at least one of: information associated with a signaling radio bearer SRB to be configured by the target DU or information associated with a data radio bearer DRB to be configured by the target DU, and

27. The method of claim 25, wherein the CU has a packet data convergence protocol PDCP function and an RRC function, and

wherein the target DU has a physical layer function, a medium access control MAC function, and a radio link control RLC function.

28. The method of claim 25, wherein the second message further includes a cell radio network temporary identity (C-RNTI) allocated by the target DU for the terminal.

29. The method of claim 25, wherein the first message further comprises terminal wireless capability information.

30. A target distribution unit, DU, of a base station, the base station comprising a central unit, CU, and a plurality of DUs, the target DU of the base station comprising:

a transceiver; and

a processor coupled with the transceiver and configured to control to:

31. The target DU of claim 30, wherein the first message further includes at least one of: information associated with a signaling radio bearer SRB to be configured by the target DU or information associated with a data radio bearer DRB to be configured by the target DU, and

32. A target DU according to claim 30, wherein the CUs have packet data convergence protocol PDCP and RRC functions, and

33. The target DU of claim 30, wherein the second message further includes a cell radio network temporary identity (C-RNTI) allocated by the target DU for the terminal.

34. The target DU of claim 30, wherein the first message further includes terminal wireless capability information.