CN109819491B

CN109819491B - Handover control method, base station, and storage medium

Info

Publication number: CN109819491B
Application number: CN201910217417.6A
Authority: CN
Inventors: 张源; 王放; 罗斐琼; 盛云鹏
Original assignee: Extradimen Technology Beijing Co ltd
Current assignee: Extradimen Technology Beijing Co ltd
Priority date: 2019-03-21
Filing date: 2019-03-21
Publication date: 2021-07-06
Anticipated expiration: 2039-03-21
Also published as: CN109819491A

Abstract

The invention provides a switching control method, a base station and a storage medium. The switching control method comprises the following steps: determining whether a handover related to the first connection needs to be performed based on a measurement report of the user equipment; the user equipment performs data transmission with a first base station through the first connection and performs data transmission with a second base station through a second connection; performing the handover if the handover needs to be performed; in the process of executing the handover, if a modification request which is from the second base station and is related to the first base station is received, determining whether the modification request conflicts with the handover; and canceling the handover and resuming the first connection before performing the handover to perform data transmission between the user equipment and the first base station, if there is a collision. By the scheme, when switching conflict occurs, the multi-connection state can be kept, the service continuity is maintained, and the user throughput is ensured.

Description

Handover control method, base station, and storage medium

Technical Field

The present invention relates to the field of multi-connection communication technologies, and in particular, to a handover control method, a base station, and a storage medium.

Background

With the development of technology, fifth generation (abbreviated as 5G) networks have started to be put into operation gradually. A Long Term Evolution (LTE) network and a 5G network, which are represented by a fourth generation (abbreviated as 4G), will coexist for a period of time. In the case of coexistence of LTE and 5G networks, the multi-connection technology is regarded as an important technical means for improving connection robustness and reliability. In the 5G multi-connection technology, a User Equipment (UE) improves throughput and mobility robustness by maintaining connection and communicating with an LTE base station and a 5G base station simultaneously. Fig. 1 shows a schematic diagram of LTE and 5G system connectivity.

As shown in fig. 1, an eNB (E-utran nodeb: Evolved universal terrestrial radio access network node B) as a macro base station in an LTE network and an en-gNB as a 5G base station are connected through an X2 interface, and the en-gNB is connected to an EPC (Evolved Packet Core) system of a Core network of LTE through S1 and S1-U interfaces. In this case, the en-gbb serving as the 5G base station only provides 5G air interface resources, and the backhaul network of the base station is accessed to the EPC side of the LTE core network for communication and data transmission.

In the dual connectivity of 5G and LTE, the connection between the UE and the eNB as the macro base station of LTE is the main connection, and the air interface includes control plane message transmissions of SRB1(Signaling Radio Bearer), SRB2, and SRB0, including measurement report upload, handover command transmission, and the like. The connection between the UE and the 5G base station en-gbb is the first connection, and the air interface includes SRB3 and can only be used to transmit measurement reports and RRC connection reconfiguration procedures (including mobility control).

Fig. 2 shows an architecture diagram of a 5G base station. As an architecture of an en-gNB of a 5G base station, as shown in FIG. 2, the base station of the en-gNB includes a gNB-CU (gNB-Central Unit: gNB centralized control Unit) and a plurality of gNB-DUs (gNB-Distributed Unit: gNB-Distributed control Unit), and one gNB-DU can be connected to only one gNB-CU. The gNB-CU can be further divided into a gNB-CU-CP (Control Plane) and a gNB-CU-UP (User Plane). The gNB-DU is connected with the gNB-CU-CP through an F1 interface.

In the current 5G and LTE multi-connection handover process, the mobility control of LTE connection is in charge of the LTE base station, and the mobility control of the 5G base station can be controlled and completed by the 5G base station itself without notifying the LTE base station on the premise that the SRB3 is established, so that a situation of interruption of a process initiated by the LTE base station may occur in the mobility handover process of the 5G base station.

The following briefly describes the multi-connection mobility handover procedure of the 5G and LTE base stations in the prior art by taking the intra-gbb/intra-DU handover as an example. Fig. 3 shows a schematic flow of intra-gbb/intra-DU handover in case of multi-connectivity for existing 5G and LTE base stations.

In step S301, the 5G UE sends a measurement report to the gNB-DU through the SRB3 of the 5G air interface. In step S302, after receiving the measurement report sent by the UE, the gNB-DU reports the measurement report to the gNB-CU-CP through an uplink RRC (Radio Resource Control) message via the F1 interface. In step S303, the gNB-CU-CP determines to trigger intra-gNB/intra-DU handover based on the received measurement report of the UE. For example, when the received measurement report of the UE indicates that the channel quality of the current primary cell of the UE is already worse than the channel quality of another cell within the gNB-DU, the gNB-CU-CP determines to trigger a primary cell handover within the gNB-DU. In step S304, the gNB-CU-CP sends a bearer context modification request to the gNB-CU-UP informing the gNB-CU-UP that the uplink data transmission channel needs to be updated for the UE. The gNB-CU-UP allocates a new UpLink F1-U interface transport layer address, namely, an UL GTP TEID (UpLink GPRS Tunnel Protocol Tunnel Endpoint Identifier: UpLink GPRS Tunnel Protocol Tunnel terminal Identifier) to the UE. After the gNB-CU-UP allocates a new uplink F1-U interface transport layer address for the UE, the gNB-CU-UP sends a bearer context modification response to the gNB-CU-CP informing the gNB-CU-CP of the new uplink F1-U interface transport layer address allocated for the UE at step S305. After receiving the bearer context modification response from the gNB-CU-UP, the gNB-CU-CP sends a UE context modification request to the gNB-DU, informing the gNB-DU to allocate a new DownLink F1-U interface transport layer address, i.e., DL GTP TEID (DownLink GPRS Tunnel Protocol Identifier: DownLink GPRS Tunnel Protocol Tunnel terminal Identifier and air interface resource of a new target cell for handover) to the UE at step S306. the gNB-DU receives the UE context modification request, allocates a new DownLink F1-U interface transport layer address to the UE and prepares air interface resource of a new target cell for handover, and sends a UE context modification response to the gNB-CU-CP at step S307, informing the gNB-CU-CP that the UE has been allocated a new DownLink F1-U interface transport layer address and an air interface resource of a target cell for handover After the allocated new downlink F1-U interface transport layer address and the air interface resource of the target cell prepared for handover are allocated, in step S308, the gNB-CU-CP sends a bearer context modification request to the gNB-CU-UP again, notifies the gNB-CU-UP of the new downlink F1-U interface transport layer address allocated by the gNB-DU for the UE, and notifies the gNB-CU-UP of stopping data transmission. The gNB-CU-UP sends a bearer context modification response to the gNB-CU-CP confirming that data transmission has ceased. After receiving the bearer context modification response sent by the gNB-CU-UP, the gNB-CU-CP suspends the bearer in step S310. At this point, the switching preparation work is completed.

Thereafter, the gNB-CU-UP sends a handover command to the gNB-DU via downlink RRC message transmission at step S311. In the prior art, the gNB-CU-CP does not know how to handle the modification request message from the MeNB (represented by the question marked box in fig. 3), since the prior art protocol does not support the handover cancellation and collision resolution mechanism, a possible solution is to release the 5G connection directly, but this would lead to service interruption. In step S312, the gNB-DU sends an RRC connection reconfiguration message to the UE through the SRB3 over the 5G air interface, so as to forward the handover command to the UE. Then, in step S313, the UE and the gNB-DU enter the random access procedure, and after the UE completes handover, in step S314, the UE sends an RRC connection reconfiguration complete message to the gNB-DU to notify that the handover of the gNB-DU is complete. In step S315, the gNB-DU sends an uplink RRC message transmission to the gNB-CU-CP and replies a handover complete command to the gNB-CU-CP. At this point, the handover is completed.

Since the above handover procedure is completed in the 5G base station through the SRB3 without notifying the LTE base station, the en-gNB may receive a SgNB (second base station) modification request triggered from the LTE master base station in the handover procedure. In this case, since the traffic priority of the LTE base station is higher than that of the 5G base station, the gNB-CU-CP needs to preferentially perform the modification request from the LTE base station. At this time, the gNB-CU-CP can only select to release the current 5G connection, and then quit the multi-connection and return to the single-connection state, thereby causing service interruption and affecting user experience.

Disclosure of Invention

In view of the above, embodiments of the present invention provide a handover control method, a base station and a storage medium, which are intended to solve one or more of the disadvantages in the prior art and at least provide a useful choice.

To achieve the object of the present invention, embodiments of the present invention provide the following aspects:

according to a first aspect of the present invention, there is provided a handover control method applicable to multiple connections, comprising: determining whether a handover related to the first connection needs to be performed based on a measurement report of the user equipment; the user equipment performs data transmission with a first base station through the first connection and performs data transmission with a second base station through a second connection; performing the handover if the handover needs to be performed; in the process of executing the handover, if a modification request which is from the second base station and is related to the first base station is received, determining whether the modification request conflicts with the handover; and canceling the handover and resuming the first connection before performing the handover to perform data transmission between the user equipment and the first base station, if there is a collision.

In some embodiments, the modification request is received if a new upstream F1-U interface transport layer address has been allocated for the user equipment in performing the handover; canceling the handover and resuming the first connection prior to performing the handover, comprising: sending a first handover cancel request to a user plane of a centralized control unit of the first base station to instruct the user plane to delete the allocated new uplink F1-U interface transport layer address and to resume the uplink F1-U interface transport layer address before the handover is performed.

In some embodiments, the modification request is received if a new downlink F1-U interface transport layer address has been allocated for the user equipment and new radio resources have been prepared for the handover in performing the handover; canceling the handover and resuming the first connection prior to performing the handover, further comprising: sending a second handover cancel request to the decentralized control unit of the first base station to instruct the decentralized control unit to release the allocated new downlink F1-U interface transport layer address and the new radio resource that has been prepared for the handover.

In some embodiments, the modification request is received in a case where the user plane of the centralized control unit of the first base station has been informed in performing the handover that the user equipment has been allocated the new downlink F1-U interface transport layer address; canceling the handover and resuming the first connection prior to performing the handover, further comprising: informing the user plane of the centralized control unit of the first base station that the allocated transport layer address of the new downlink F1-U interface has been released.

In some embodiments, the handover control method further comprises: performing a modification associated with the first base station according to the modification request during data transmission between the user equipment and the first base station using the recovered first connection; after the modification is performed, re-determining whether a handover related to the first connection needs to be initiated based on a measurement report of the user equipment.

In some embodiments, the handover control method further comprises: and combining the modification request and the handover together and informing the user equipment to synchronously execute the modification request and the handover respectively under the condition that the modification request does not conflict with the handover.

In some embodiments, merging the modification request with the handover to notify the user equipment comprises: combining the command related to the modification request and the command of the handover into a Radio Resource Control (RRC) connection reconfiguration message by using the user plane of the centralized control unit of the first base station, and notifying the user equipment through a radio signaling bearer 1(SRB1) of the second base station.

In some embodiments, the handover comprises handing over a primary cell of the first connection; the modification request comprises modifying a configuration of a primary cell of the first connection.

In some embodiments, determining whether the modification request conflicts with the handover comprises: determining whether there is a conflict between the user equipment configuration required in the modification request and the user equipment configuration required in the handover.

In some embodiments, the first base station is a 5G base station; and the second base station is an LTE base station.

According to another aspect of the present invention, there is provided a base station, which is a first base station, comprising a processor, a memory and a transceiver unit, wherein the memory is used for storing computer instructions, the processor is used for executing the computer instructions stored in the memory to control the transceiver unit to transmit and receive signals, and the base station is used for implementing the handover control method according to the above embodiments when the processor executes the computer instructions stored in the memory.

According to another aspect, the present invention also provides a storage medium having stored thereon computer program code which when executed implements a handover control method as described above.

According to the switching control method, the conflict between the modification request of the LTE base station and the mobility switching of the 5G can be solved, so that the multi-connection state can be maintained to maintain the service continuity and the user throughput can be ensured when the switching conflict occurs.

Drawings

The above and other objects, features and advantages of the present invention will be more readily understood by reference to the following description of the embodiments of the present invention taken in conjunction with the accompanying drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. For purposes of illustrating and describing some portions of the present invention, corresponding parts may be exaggerated in the drawings, i.e., made larger relative to other components in an exemplary apparatus actually manufactured according to the present invention. In the drawings, the same or corresponding technical features or components will be denoted by the same or corresponding reference numerals.

Fig. 1 shows a schematic diagram of the connection of the LET and 5G systems;

fig. 2 shows an architectural schematic of a 5G base station;

fig. 3 shows a schematic flow diagram of intra-gbb/intra-DU handover in case of multi-connectivity for existing 5G and LTE base stations;

FIG. 4 shows a flow chart of a handover control method in case of a collision according to an embodiment of the invention;

FIG. 5 shows a flow chart of a handover control method without collision according to an embodiment of the invention;

FIG. 6 is a flow chart illustrating an application example of the handover control method according to the embodiment of the present invention;

fig. 7 is a flowchart showing another application example of the handover control method according to the embodiment of the present invention; and

fig. 8 shows a schematic block diagram of a base station in an embodiment of the invention.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of the manner in which the principles of the invention may be employed. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes many variations, modifications and equivalents within the spirit and scope of the appended claims.

It should be noted that the figures and description omit representation and description of components and processes that are not relevant to the present invention and that are known to those of ordinary skill in the art for the sake of clarity.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.

In a multi-connection scenario, a User Equipment (UE) transmits data with a first base station over a first connection and with a second base station over a second connection. When the first base station receives a modification request from the second base station in the process of performing mobility handover of the UE, because the mobility handover process of the first base station does not notify the second base station, there is a possibility of a conflict between the mobility handover of the first base station and the modification request from the second base station. When a conflict occurs, because the second base station is used as a main base station and the service priority of the second base station is higher than that of the first base station, the first base station needs to execute a modification command from the second base station first, so that the first base station can only select to release the current first connection, and the UE exits from the multi-connection state and returns to the single-connection state.

In order to solve the problem of conflict between mobility handover of a first base station and a modification request from a second base station in a multi-connection situation, the invention provides a new handover control method, which is divided into two cases when the first base station receives the modification request from the second base station in the handover process related to UE mobility:

in the first case: modification request and handover conflict

Firstly, the first base station carries out switching cancellation operation, if the first base station allocates new wireless resources for the UE in the switching preparation process, the allocated new wireless resources are released to be used by other UEs, meanwhile, data transmission before switching is recovered, and then after the modification operation of the second base station is executed, whether a mobility switching process is restarted or not is determined according to a measurement report of the UE.

In the second case: there is no conflict between modification request and handover

The first base station combines the modification command from the second base station with the handover command to inform the UE. At this time, the UE receives two process operations through a signaling, the first is a modification command of the second base station, the second is a mobility handover command of the first base station, and the two operation processes are independently performed at the air interfaces of the second base station and the first base station at the same time.

Therefore, when switching conflict occurs, the multi-connection state can be continuously maintained, the service continuity is maintained, and the user throughput is ensured. In some examples, the new radio resource allocated to the UE by the first base station side in the handover preparation process can be released for other UEs, so that the resource utilization rate is improved. And under the condition of no conflict, the two processes are combined together to inform the UE to simultaneously carry out the mobility switching of the first base station and the modification process of the second base station, so that the signaling efficiency is improved.

The following describes a handover control method according to an embodiment of the present invention with reference to fig. 4, taking as an example that the first base station is a 5G base station, the second base station is a 4GLTE base station, the LTE base station is a master base station (also referred to as MeNB), and the 5G base station is a secondary base station (also referred to as SgNB). Fig. 4 shows a handover control method in the case where there is a conflict.

As shown in fig. 4, step S410 determines whether a handover related to a first connection through which the user equipment performs data transmission with a first base station (5G base station) and a second base station (4GLTE base station) through a second connection needs to be performed based on a measurement report of the user equipment. Specifically, it may be determined to perform handover related to the first connection based on a measurement report from the UE using an en-gNB (also referred to as SgNB) as a 5G base station. In some examples, the measurement report may be sent by the UE to the gNB-DU of the en-gNB over a 5G air interface SRB3, and then the gNB-DU is sent to the en-gNB-CU-CP via an uplink RRC message. In some examples, the handover may include handing over a primary cell of the first connection. For example, when the en-gNB receives a measurement report for the UE indicating that the UE's current primary cell channel quality is already worse than the channel quality of another cell within the gNB-DU, the gNB-CU-CP may determine to trigger a primary cell handover within the gNB-DU.

In step S420, in case that the handover needs to be performed, the handover is performed; in the process of performing the handover, if a modification request related to the first base station (5G base station) is received from the second base station (4G lte base station), it is determined whether the modification request conflicts with the handover. Specifically, the en-gNB may be utilized to determine whether the modification request conflicts with the handover in the case of receiving a modification request related to the SgNB (i.e., en-gNB) from the MeNB in performing the handover. As an example, it may be determined whether there is a conflict between the user equipment configuration required in the modification request and the user equipment configuration required in the handover. In some examples, the modification request may include modifying a configuration of a primary cell of the first connection. For example, the handover the en-gbb is performing is to change the primary cell (Pscell) of the UE, e.g. from cell 1 to cell 2, while the modification request from the MeNB requires modifying the configuration of Pscell, i.e. modifying the configuration of cell 1. Therefore, there is a conflict between the handover and the modification request.

In step S430, in case of a collision, canceling the handover and resuming the first connection before performing the handover for data transmission between the user equipment and the first base station. In particular, in case of a collision, the en-gbb may be utilized to cancel the handover operation and resume data transmission over the first connection before the UE handover.

In some examples, upon receiving the modification request, the en-gbb has not allocated new radio resources for the UE in the handover preparation phase, e.g., before step S304 shown in fig. 3. At this point, the en-gbb need only ignore the decision made to initiate the handover, i.e., cancel the handover operation, and maintain the current data transmission with the UE over the first connection.

In some examples, the en-gbb has allocated new radio resources for the UE in the handover preparation phase upon receipt of the modification request. For example, after the gbb-DU has prepared the radio resources of the new target cell for the handover in the handover control method shown in fig. 3. At this time, the en-gbb may release new radio resources that have been prepared for the handover while canceling the handover, so that the radio resources may be used by other UEs, thereby improving resource use efficiency.

Specifically, in some examples, according to the stage of the handover preparation procedure when the modification request is received, the cancellation operation may be performed in the following cases:

1) the UE has been assigned a new uplink F1-U transport layer address, but has not been assigned a new downlink F1-U transport layer address and radio resources

This case corresponds to the case after step S304 and before step S306 in fig. 3. In this case, in step S430, the specific implementation of canceling the handover and resuming the first connection before performing the handover may include: sending a first handover cancel request to a user plane (gNB-CU-UP) of a centralized control unit of the first base station to instruct the user plane to delete the allocated new uplink F1-U interface transport layer address and to resume the uplink F1-U interface transport layer address before the handover is performed. Specifically, a first handover cancel message may be sent to the gNB-CU-UP using a control plane (gNB-CU-CP) of the centralized control unit of the first base station instructing the gNB-CU-UP to delete the assigned new uplink F1-U interface transport layer address and resume data transmission over the first connection prior to handover. The gNB-CU-CP confirms that the handover has been cancelled and resumes data transmission over the first connection prior to the UE handover based on a first handover cancel confirmation from the gNB-CU-UP confirming that the assigned new upstream F1-U interface transport layer address has been deleted.

2) The UE has been assigned a new uplink F1-U transport layer address and a downlink F1-U transport layer address, but the downlink F1-U transport layer address has not yet been informed of the gNB-CU-UP

This case corresponds to the case after step S306 and before step S308 in fig. 3. In this case, in the specific implementation of canceling the handover and resuming the first connection before the handover is performed in step S430, in addition to performing the first handover message in case 1, the following steps need to be performed:

sending a second handover cancel request to the decentralized control unit (gNB-DU) of the first base station to instruct the decentralized control unit (gNB-DU) to release the allocated new downlink F1-U interface transport layer address and the new radio resource prepared for the handover. Specifically, a second handover cancel request may be sent to the gNB-DU by the gNB-CU-CP instructing the gNB-DU to release the allocated new downlink F1-U interface transport layer address and radio resources of the new target cell already prepared for the handover. Then, the gNB-CU-CP resumes data transmission for the UE based on the pre-handover downlink F1-U interface transport layer address based on confirmation from the gNB-DU that the allocated new downlink F1-U interface transport layer address has been released and a handover cancel confirmation of the new radio resource that has been prepared for the handover.

That is, in this case, the gNB-CU-CP not only notifies the gNB-DU to release the allocated downlink F1-U transport layer address and the radio resource of the new target cell that has been prepared for handover, but also needs to notify the gNB-CU-UP to delete the allocated uplink F1-U transport layer address.

3) The UE has been assigned a new uplink F1-U transport layer address and a downlink F1-U transport layer address, and the downlink F1-U transport layer address has notified the gNB-CU-UP

This case corresponds to the handover preparation process having been completed, i.e., after step S308 in fig. 3. In this case, in the specific implementation manner that cancels the handover and resumes the first connection before performing the handover in step S430, in addition to performing all the steps in case 2, the method further includes: informing the user plane (gNB-CU-UP) of the centralized control unit of the first base station that the allocated transport layer address of the new downlink F1-U interface has been released. For example, a first handover cancel message sent by the gNB-CU-CP to the gNB-CU-UP may be utilized to inform the gNB-CU-UP that the assigned new downstream F1-U interface transport layer address has been released.

As another example, the gNB-CU-CP first informs the gNB-DU to release the allocated downlink F1-U transport layer address and the radio resources of the new target cell that has been prepared for the handover, then informs the gNB-CU-UP to delete the allocated uplink F1-U transport layer address and resume data transmission based on the first connection before the handover, and informs the gNB-CU-CP that the new downlink F1-U transport layer address that has been prepared for the handover has been released.

After the handover cancel operation is completed, the handover control method further includes: performing a modification related to the first base station (5G base station) according to the modification request during data transmission between the user equipment and the first base station (5G base station) using the recovered first connection. In particular, the en-gNB may be utilized to perform modifications related to the modification request, i.e. the modification procedure of the SgNB base station from the MeNB.

After the modification related to the modification request is completed, the handover control method further includes: re-determining whether a handover related to the first connection needs to be initiated based on the measurement report of the user equipment. Specifically, the en-gbb may be utilized to re-determine whether to initiate handover based on a measurement report of a newly received UE. If it is determined that handover is initiated, handover is re-performed.

According to the switching control method provided by the embodiment of the invention, when the switching operation conflicts with the modification request, the switching operation is cancelled, so that the UE keeps a multi-connection state, the service continuity is maintained and the user throughput is ensured.

In some examples, the radio resources prepared for handover by the en-gbb in the handover preparation phase can be released for use by other UEs, improving resource usage.

Fig. 5 illustrates a handover control method in case of no collision according to an embodiment of the present invention. Steps S510 and S520 are the same as steps S410 and S420 in fig. 4, respectively, and are not described again here. The difference is that the modification request from the MeNB related to the en-gbb does not conflict with the handover request.

At this time, in step S530, the modification request and the handover are merged together, and the user equipment is notified to synchronously perform the modification request and the handover, respectively. The handover and modification request can be merged together by the en-gbb, by knowing the UE. The specific implementation of the step S530 may include: combining the command related to the modification request and the command for handover into a Radio Resource Control (RRC) connection reconfiguration message by using a user plane (gNB-CU-UP) of the centralized control unit of the first base station, and notifying the user equipment through a radio signaling bearer 1(SRB1) of the second base station (4 GLTE). Specifically, after the en-gbb completes the handover preparation, the modification command associated with the modification request from the MeNB may be combined with the handover command into one RRC connection reconfiguration message, which is notified to the UE via the SRB1 of the MeNB. And then performs a handover operation with the UE. At this time, the UE receives two commands through an RRC signaling, one is a modification command of the MeNB base station, and the other is a handover command of the en-gNB. The UE independently executes the two commands at the air interfaces of the MeNB and the en-gNB at the same time.

Since two commands are transmitted to the UE through one signaling, signaling efficiency is improved.

Fig. 6 is a flowchart illustrating an application example of the handover control method according to the embodiment of the present invention.

The step S601 of the UE sending the measurement report, the step S602 of the gNB-DU forwarding the measurement report to the gNB-CU-CP, and the step S603 of the gNB-CU-CP triggering the handover based on the measurement report confirmation are the same as those described with reference to fig. 3, and the details thereof are omitted here.

In step S604, the en-gNB performs a handover preparation process based on the SRB3, which can be specifically seen from step S304 to step S309 in fig. 3.

In step S605, when the en-gNB receives the SgNB (i.e., en-gNB) modification request from the MeNB after handover preparation is completed.

In step S606, if the received modification request conflicts with the currently performed mobility handover, in step S607, the gNB-CU-CP sends a downlink handover cancel request to the gNB-DU through the F1 interface, where the downlink handover cancel request may include the ID (identity) of the UE and an operation instruction to cancel the handover, and instructs the gNB-DU to delete the transport layer address of the new downlink F1-U interface, i.e., DL GTP TEID, allocated to the UE and the radio resource of the new target cell prepared for the handover, and at the same time, resumes data transmission based on the TEID before the handover.

After the gbb-DU completes the relevant operation, it sends a downlink handover cancel acknowledgement to the gbb-CU-CP through the F1 interface at step S608, confirming that the transport layer address of the new downlink F1-U interface allocated for the UE and the radio resource of the new target cell prepared for the handover have been released.

At step S609, the gNB-CU-CP sends an uplink handover cancel request to the gNB-CU-UP through the E1 interface, the uplink handover cancel request may include the UE ID and an indication to cancel the handover, instruct the gNB-CU-UP to delete the newly allocated uplink F1-U transport layer address while resuming data transmission based on the uplink F1-U transport layer address before the handover, and notify the gNB-CU-UP that the allocated new downlink F1-U transport layer address for the UE is released.

After the relevant operations are completed, the gNB-CU-UP sends an uplink switching cancellation confirmation to the gNB-CU-CP through the E1 interface in step S610, confirms that the transport layer address of the new uplink F1-U interface allocated for the UE has been deleted, and resumes data transmission based on the transport layer address of the uplink F1-U before switching.

By this point, the handover cancel operation is completed, and the UE maintains both the first connection with the en-gbb before handover and the second connection with the MeNB, i.e. the UE still maintains multi-connectivity.

Although it is shown in the above example that the step S605 of receiving the SgNB modification request from the MeNB is received after the handover preparation is completed, the step may be received in the handover preparation process.

When the modification request is received during the handover preparation procedure, for example, when the gbb-DU is allocated a new downlink F1-U transport layer address and radio resources of a new target cell have been prepared for handover but the gbb-CU-CP has not been notified yet, in step S609, the gbb-CU-UP is only instructed to delete the newly allocated uplink F1-U transport layer address without notifying that the new downlink F1-U transport layer address allocated for the UE has been released, and at the same time, data transmission based on the uplink F1-U transport layer address before handover is resumed.

Steps S607 and S608 may not be performed when the gNB-DU has not allocated the downlink F1-U transport layer address and the radio resource of the target cell prepared for handover. At this time, the gNB-CU-CP is not notified in step S609 that the new downlink F1-U transport layer address allocated for the UE has been released.

After the handover cancellation is completed, the gNB-CU-CP executes a modification request from the MeNB in step S611. After the modification request is completed, the gNB-CU-CP re-determines whether to trigger a new handover based on the measurement report from the UE at step S612.

Fig. 7 is a flowchart illustrating another application example of the handover control method according to the embodiment of the present invention.

Steps S701 to S705 are the same as steps S601 to S605, and are not described again here. It is determined in step S706 that the received SgNB modification request does not conflict with the current handover. After the handover preparation phase is completed, the handover preparation procedure based on SRB3 may be completed before sending the handover request response to the MeNB, and separate signaling may not be needed. In step S707, the gNB-CU-CP combines the modification command and the handover command corresponding to the modification request, and transmits a SgNB modification request response to the MeNB, notifying the MeNB. In step S708, the MeNB notifies the UE of the command related to the modification request together with the command for handover through an RRC reconfiguration message via the SRB1 interface. Specifically, the gNB-CU-CP may be responsible for generating a handover command, replying to a modification request from the MeNB, for example, accepting one configuration, rejecting another configuration, replying by the MeNB through the gNB-CU-CP, generating a corresponding RRC message, combining the handover command with the RRC message, and sending the combined handover command to the UE, so that the MeNB may complete the final combination. The UE receives two commands through one RRC signaling, wherein one command is a modification command of the MeNB base station, and the other command is a switching command of the en-gNB. The UE independently executes the two commands at the air interfaces of the MeNB and the en-gNB at the same time. After the UE completes the modification command and the handover command, the MeNB is notified by an RRC reconfiguration complete message in step S709. Alternatively, the UE may notify the MeNB and the engNB that the related operations have been completed through two RRC reconfiguration complete messages, respectively, after the command related to the modification request and the command of the handover are each completed.

In some embodiments of the present invention, a base station is further provided, and as shown in fig. 8, the base station may be the first base station (en-gbb) described above. The en-gbb may comprise a processor 810, a memory 820, and a transceiver unit, which may comprise a receiver 830 and a transmitter 840, the processor 810, the memory 820, the receiver 830 and the transmitter 840 may be connected by a bus system, the memory 820 may be configured to store computer instructions, and the processor 810 may be configured to execute the computer instructions stored in the memory 820 to control the transceiver unit to transmit and receive signals, thereby implementing the steps performed by the en-gbb in the handover control method described above with reference to fig. 4 to 7.

In some embodiments of the present invention, the user equipment may comprise a processor, a memory, and a transceiving unit, the transceiving unit may comprise a receiver and a transmitter, the processor, the memory, the receiver and the transmitter may be connected by a bus system, the memory is used for storing computer instructions, and the processor is used for executing the computer instructions stored in the memory to control the transceiving unit to transmit and receive signals, thereby implementing the steps performed by the user equipment in the handover control method described above with reference to fig. 4 to 7.

As an implementation manner, the functions of the receiver and the transmitter in the present invention may be implemented by a transceiver circuit or a dedicated chip for transceiving, and the processor may be implemented by a dedicated processing chip, a processing circuit or a general-purpose chip.

As another implementation manner, a manner of using a general-purpose computer to implement the base station provided in the embodiment of the present invention may be considered. That is, program code that implements the functions of the processor, receiver, and transmitter is stored in the memory, and a general-purpose processor implements the functions of the processor, receiver, and transmitter by executing the code in the memory.

The present invention also provides a storage medium, on which computer program code may be stored, which may be a tangible storage medium such as an optical disc, a usb disk, a floppy disk, a hard disk, etc., when the program code is executed, may implement the various embodiments of the handover control method described with reference to fig. 4 to 7.

Those of ordinary skill in the art will appreciate that the various illustrative elements and method steps described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations of both. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied in software executed by hardware (a logic device such as a computer). The software, when executed, may cause the hardware (computer or other logic device) to implement the methods or its constituent steps described above, or cause the hardware (computer or other logic device) to function as apparatus components of the invention described above.

The software may be disposed in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

The embodiments described above are exemplary rather than limiting and those skilled in the art will appreciate that various modifications and alterations can be made in the spirit of the invention and that such modifications and alterations are also within the scope of the invention.

Claims

1. A handover control method for multiple connections, the handover control method comprising:

determining whether a handover related to the first connection needs to be performed based on a measurement report of the user equipment; the user equipment performs data transmission with a first base station through the first connection and performs data transmission with a second base station through a second connection;

performing the handover if the handover needs to be performed; in the process of executing the handover, if a modification request which is from the second base station and is related to the first base station is received, determining whether the modification request conflicts with the handover; and

and in the case of conflict, canceling the handover and resuming the first connection before the handover is performed, so as to perform data transmission between the user equipment and the first base station.

2. The handover control method according to claim 1, wherein the modification request is received in a case where a new upstream F1-U interface transport layer address has been allocated to the user equipment in the course of performing the handover;

canceling the handover and resuming the first connection prior to performing the handover, comprising:

sending a first handover cancel request to a user plane of a centralized control unit of the first base station to instruct the user plane to delete the allocated new uplink F1-U interface transport layer address and to resume the uplink F1-U interface transport layer address before the handover is performed.

3. The handover control method according to claim 2, wherein the modification request is received in a case where a new downlink F1-U interface transport layer address has been allocated to the user equipment and a new radio resource has been prepared for the handover in the course of performing the handover;

canceling the handover and resuming the first connection prior to performing the handover, further comprising:

sending a second handover cancel request to the decentralized control unit of the first base station to instruct the decentralized control unit to release the allocated new downlink F1-U interface transport layer address and the new radio resource that has been prepared for the handover.

4. The handover control method according to claim 3, wherein the modification request is received in a case where a user plane of a centralized control unit of the first base station has been notified in the process of performing the handover that the new downlink F1-U interface transport layer address has been allocated for the user equipment;

informing the user plane of the centralized control unit of the first base station that the allocated transport layer address of the new downlink F1-U interface has been released.

5. The handover control method according to any one of claims 1 to 4, further comprising:

performing a modification associated with the first base station according to the modification request during data transmission between the user equipment and the first base station using the recovered first connection;

after the modification is performed, re-determining whether a handover related to the first connection needs to be initiated based on a measurement report of the user equipment.

6. The handover control method according to claim 1, further comprising:

and combining the modification request and the handover together and informing the user equipment to synchronously execute the modification request and the handover respectively under the condition that the modification request does not conflict with the handover.

7. The handover control method according to claim 6, wherein combining the modification request with the handover to notify the UE comprises:

combining the command related to the modification request and the command of the handover into a Radio Resource Control (RRC) connection reconfiguration message by using the user plane of the centralized control unit of the first base station, and notifying the user equipment through a radio signaling bearer 1(SRB1) of the second base station.

8. The handover control method according to claim 1, wherein the handover comprises handing over a primary cell of the first connection; the modification request comprises modifying a configuration of a primary cell of the first connection.

9. The handover control method of claim 1, wherein determining whether the modification request conflicts with the handover comprises:

determining whether there is a conflict between the user equipment configuration required in the modification request and the user equipment configuration required in the handover.

10. The handover control method according to claim 1, wherein the first base station is a 5G base station; the second base station is an LTE base station.

11. A base station, wherein the base station is a first base station and comprises a processor, a memory and a transceiver unit, wherein the memory is configured to store computer instructions, the processor is configured to execute the computer instructions stored in the memory to control the transceiver unit to transmit and receive signals, and the base station is configured to perform the handover control method according to any one of claims 1 to 10 when the processor executes the computer instructions stored in the memory.

12. A storage medium having stored thereon computer program code which when executed implements a handover control method as claimed in any one of claims 1 to 10.