WO2017092021A1

WO2017092021A1 - Method and apparatus for switching cell

Info

Publication number: WO2017092021A1
Application number: PCT/CN2015/096367
Authority: WO
Inventors: 杨勇
Original assignee: 华为技术有限公司
Priority date: 2015-12-03
Filing date: 2015-12-03
Publication date: 2017-06-08
Also published as: CN108293210A; CN108293210B

Abstract

The invention relates to the technical field of mobile communications, and more particularly to a method and an apparatus for cell switching, for solving a technical problem of resource wastage caused by retransmitting a switching command to a user equipment (UE). In an embodiment of the invention, a first access network apparatus can detect whether a terminal apparatus transmits a preamble sequence to a second access network apparatus after the first access network apparatus transmits a switching command to the terminal apparatus. If it is detected that the terminal apparatus transmits the preamble sequence to the second access network apparatus, the first access network apparatus can determine that the terminal apparatus has received the switching command. Therefore, the first access network apparatus does not need to transmit the switching command to the terminal apparatus again, avoiding invalid retransmission of the switching command and reducing transmission resources.

Description

Cell switching method and device

Technical field

The present invention relates to the field of mobile communications technologies, and in particular, to a cell switching method and device.

Background technique

When the user equipment (UE) is to perform the cell handover, the base station sends a handover command to the UE. After receiving the handover command, the UE needs to synchronize and access the target cell as soon as possible, so that the UE may not be able to feedback to the base station. When a handover command is received (some commercial UEs may not feed back the handover command sent by the base station, but directly to the target cell for access). When the base station does not receive the feedback of the handover command, the UE may not receive the handover command, and may retransmit the handover command to the UE through the radio link control (RLC) retransmission mechanism, which may cause the handover command. Invalid retransmission, wasting base station resources.

Summary of the invention

The embodiments of the present invention provide a cell handover method and device, which are used to solve the technical problem of resource waste caused by resending a handover command to a UE.

The first aspect provides a cell handover method, including:

Determining, by the first access network device, that the terminal device residing in the first cell of the first access network device is about to switch to the second cell in the second access network device;

The first access network device sends a handover command to the terminal device, where the handover command is used to instruct the terminal device to switch to the second cell;

If the first access network device does not receive the feedback from the terminal device for the handover command, the first access network device detects whether the terminal device passes the second cell to the second connection The network access device sends a preamble sequence;

If the first access network device detects that the terminal device has sent the preamble sequence to the second access network device by using the second cell, the first access network device stops to the terminal The device resends the switching command.

Generally, when the terminal device is to access the new cell, the preamble sequence is sent to the new cell. Therefore, in the embodiment of the present invention, the first access network device does not receive the handover command after sending the handover command to the terminal device. The first access network device may detect whether the terminal device sends a preamble sequence to the second access network device (ie, the target access network device), and if the terminal device has detected that the terminal device has been connected to the second connection, After the network access device sends the preamble sequence, the first access network device can determine that the terminal device has received the handover command (because the terminal device sends the Preamble to the target access network device after receiving the handover command), therefore, the first The access network device does not need to resend the Preamble to the terminal device, avoiding invalid retransmission of the handover command and saving transmission resources.

With reference to the first aspect, in a first possible implementation manner of the first aspect, the method further includes:

If the first access network device does not detect that the terminal device sends the preamble sequence to the second access network device by using the second cell, the first access network device re-directs to the terminal The device sends the switching command.

If the first access network device does not detect that the terminal device sends the preamble sequence to the second access network device, the first access network device may resend the handover command to the terminal device to ensure that the terminal device can receive the handover command, thereby Perform cell handover to improve handover success rate.

With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the first access network device determines to reside in the first access network device After the terminal device in the first cell is about to switch to the second cell in the second access network device, the method further includes:

The access network device acquires an identifier and an access parameter of the terminal device.

With reference to the second possible implementation of the first aspect, in a third possible implementation manner of the first aspect, the method further includes:

The first access network device calculates an identifier of the preamble sequence sent by the terminal device according to the identifier and the access parameter of the terminal device.

The second access network device allocates the identifier of the preamble sequence to the terminal device, so that the identifier of the preamble sequence sent by the terminal device is allocated by the second access network device, and the second access network device is When the terminal device allocates the identifier of the preamble sequence, it is allocated according to the identifier of the terminal device, the access parameter, and the like. Therefore, the first access network device can obtain the identifier of the terminal device and the access parameter, so that the identifier of the preamble sequence to be sent by the terminal device can be calculated, so that the first access network device can perform detection.

With the third possible implementation of the first aspect, in a fourth possible implementation manner of the first aspect, the first access network device detects whether the terminal device passes the second cell to the The second access network device sends the preamble sequence, including:

The first access network device matches the identifier of the detected preamble sequence with the calculated identifier of the preamble sequence sent by the terminal device;

If the identifier of the detected preamble sequence matches the calculated identifier of the preamble sequence sent by the terminal device, the first access network device determines that the terminal device passes the second cell to the second interface. The network access device sends the preamble sequence.

The first access network device may receive multiple preamble sequences, and in order to detect whether the terminal device sends the preamble sequence to the second access network device, the first access network device may use the calculated preamble sequence sent by the terminal device. The identifier matches the identifier of the detected preamble sequence. If the matching is successful, it may be determined that the terminal device sends the preamble sequence to the second access network device. This matching method is also simple and easy to implement.

In a second aspect, a first access network device is provided. In a possible design, the structure of the access network device includes a processor, a transmitter, and a receiver, and the processor is configured to support an access network. The device performs the corresponding function in the method of the first aspect. The transmitter and the receiver are configured to support communication between an access network device and a terminal device, and the transmitter transmits information or instructions involved in the method of the first aspect to the terminal device, the receiver receiving terminal Information or instructions involved in the method of the first aspect of the device transmission. The access network device can also include a memory for coupling with the processor that retains the necessary program instructions and data for the access network device.

In a third aspect, a second access network device is provided, the access network device comprising means for performing the method of the first aspect.

DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly described below. It is obvious that the following drawings are only some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without paying any creative work.

FIG. 1 is a flowchart of a cell handover performed by a user equipment;

2 is a flowchart of a cell handover method according to an embodiment of the present invention;

3 is a schematic structural diagram of an access network device according to an embodiment of the present invention;

FIG. 4 is a structural block diagram of an access network device according to an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Hereinafter, some of the terms used in the present invention will be explained so as to be understood by those skilled in the art.

1) A terminal device, which is a device that provides voice and/or data connectivity to a user, for example, may include a handheld device with wireless connectivity, or a processing device connected to a wireless modem. The terminal device can communicate with the core network via a Radio Access Network (RAN) to exchange voice and/or data with the RAN. The terminal device device may include a wireless terminal device, a mobile terminal device, a Subscriber Unit, a Subscriber Station, a Mobile Station, a Remote Station, and an Access Point (AP). ), Remote Terminal, Access Terminal, User Terminal, User Agent, UE, or User Device. For example, it can be a mobile phone (or "cellular" phone), with computing of the mobile terminal device Machine, portable, pocket, handheld, computer built-in or in-vehicle mobile device. For example, Personal Communication Service (PCS) phones, cordless phones, Session Initiation Protocol (SIP) phones, Wireless Local Loop (WLL) stations, Personal Digital Assistants (Personal Digital Assistant, PDA) and other equipment.

2) An access network device, for example comprising a base station (e.g., an access point), which may refer to a device in the access network that communicates over the air interface with the wireless terminal device device over one or more sectors. The base station can be used to convert the received radio frame to an Internet Protocol (IP) packet as a router between the wireless terminal equipment and the rest of the access network, wherein the remainder of the access network can include an IP network. The base station can also coordinate attribute management of the air interface. For example, the base station may be a Radio Network Controller (RNC) or a Base Station Controller (BSC), or may be a Long Term Evolution (LTE) system or an enhanced LTE (LTE-Advanced). The evolved base station (NodeB or eNB or e-NodeB, evolutional Node B) in the LTE-A) is not limited in the embodiment of the present invention.

3) In the embodiment of the present invention, "a plurality" means two or more. "and/or", describing the association relationship of the associated objects, indicating that there may be three relationships, for example, A and/or B, which may indicate that there are three cases where A exists separately, A and B exist at the same time, and B exists separately. In addition, the character "/", unless otherwise specified, generally indicates that the contextual object is an "or" relationship.

Please refer to FIG. 1 , which describes a process in which a UE performs cell handover.

1. The user equipment sends a measurement report (Measurement Report) to the base station (eNodeB).

The base station determines whether the target cell indicated by the measurement report meets the handover threshold, and if yes, performs step 2.

2. The base station sends a handover command to the user equipment. For example, the radio resource control connection reconfiguration (RRC Connection Reconfiguration) can be used to send a handover command to the user equipment.

After that, the base station starts to wait for the feedback message sent by the user equipment for the handover command, and the general waiting period is 50 ms. If the feedback message sent by the user equipment is received within 50 ms, the base station stops. The switch command is sent to the user equipment, and the process ends. If the feedback message sent by the user equipment is not received within 50 ms, step 3 is performed.

3. The base station resends the handover command to the user equipment according to the RLC retransmission mechanism.

At present, in order to minimize the number of times the handover command is sent, the maximum number of times the handover command is retransmitted is generally 2 times.

The current mechanism may cause the following problems:

1) If the user equipment has received the handover command, but does not feed back to the base station or has time to feedback to the base station, the base station assumes that the user equipment does not receive the handover command, resulting in redundant retransmission of the handover command, which also causes a block error rate (Block Error Rate, BLER) indicators deteriorated.

2) If the user equipment does not receive the handover command twice, and the base station stops transmitting the handover command, the handover of the user equipment fails, and the handover success rate indicator of the base station is lowered.

In order to solve the problems, the technical solutions of the embodiments of the present invention are proposed, which will be described below with reference to the accompanying drawings.

Referring to FIG. 2, an embodiment of the present invention provides a cell handover method, and a process of the method is described as follows.

Step 201: The first access network device determines that the terminal device residing in the first cell of the first access network device is about to switch to the second cell in the second access network device.

Step 202: The first access network device sends a handover command to the terminal device, where the handover command is used to instruct the terminal device to switch to the second cell.

Step 203: If the first access network device does not receive the feedback of the terminal device for the handover command, the first access network device detects whether the terminal device sends the preamble sequence to the second access network device by using the second cell.

Step 204: If the first access network device detects that the terminal device has sent the preamble sequence to the second access network device by using the second cell, the first access network device stops resending the handover command to the terminal device.

Optionally, the first cell and the second cell are different cells, and the first access network device and the second access network device may be the same access network device, or may be different access network devices.

When the terminal device performs cell handover, it will go to the first access network device where the original serving cell is located. The eNodeB sends a measurement report. After receiving the measurement report, the first access network device can determine whether the target cell indicated by the measurement report meets the handover threshold. If not, the first access network device does not allow the terminal device to perform the handover. If the first access network device allows the terminal device to perform cell handover, the first access network device may send a handover command to the terminal device, and the terminal device may perform cell handover after receiving the handover command.

Generally, after receiving the handover command, the terminal device feeds back a response message for the handover command to the first access network device, so that the first access network device can know that the terminal device has received the handover command. However, according to the provisions of the protocol, the terminal device accesses the target cell as soon as possible after receiving the handover command, so that the terminal device may not send a feedback message to the first access network device after receiving the handover command, or some terminal device sets In order not to send a feedback message to the first access network device. When the terminal device accesses the target cell, the preamble sequence is sent to the target cell (that is, the target cell is sent to the access network device where the target cell is located), that is, the preamble is sent, so in the embodiment of the present invention, the terminal device can be The first access network device where the original serving cell is located detects whether the terminal device sends the Preamble. If it detects that the terminal device has sent the Preamble, it can be determined that the terminal device has received the handover command, and there is no need to resend the handover command to the terminal device. Save base station resources, and try to avoid the deterioration of BLER indicators. The resending of the handover command to the terminal device may be understood as not sending the handover command to the terminal device.

Optionally, after the first access network device detects whether the terminal device sends the preamble sequence to the second access network device by using the second cell, if the first access network device does not detect that the terminal device sends the Preamble to the second cell, Then, the first access network device can send a handover command to the terminal device again. For example, after the first access network device sends the handover command to the terminal device, the device may wait for the feedback of the terminal device for the handover command. For example, the first access network device may wait for the first duration, if the first connection is within the first duration. After the network access device receives the feedback of the terminal device for the handover command, the first access network device may determine that the terminal device receives the handover command, and the first access network device may determine that the handover command is not resent to the terminal device, but If the feedback of the terminal device for the handover command is not received within the first time period, the first access network device may detect whether the terminal device has sent the Preamble to the second access network device, if the first access network device detects Terminal device to second access network device If the Preamble is sent, the first access network device determines that the handover command is no longer retransmitted to the terminal device, and if the first access network device does not detect that the terminal device sends the Preamble to the second access network device, the first access The network device may send a handover command to the terminal device again to prevent the terminal device from failing to receive the handover command, thereby improving the handover success rate. The first time length may be, for example, 50 ms, or may be other values, such as less than 50 ms, which is not limited in the embodiment of the present invention.

Optionally, if the first access network device does not receive the feedback of the terminal device for the handover command, the first access network device may start a timer to detect whether the terminal device has accessed the second access. The network device sent the Preamble. Before the timer expires, if the first access network device detects that the terminal device sends the Preamble to the second access network device, the first access network device determines that the handover command is no longer retransmitted to the terminal device, but the timer When the timeout occurs, if the first access network device does not detect that the terminal device sends the Preamble to the second access network device, the first access network device may send the handover command to the terminal device again. The timing of the timer may be set according to the situation, for example, may be set to 50 ms, or may be set to other values, which is not limited in the embodiment of the present invention.

Optionally, if the number of times that the first access network device sends the handover command to the terminal device reaches the maximum number of allowed handover command retransmissions, the first access network device may stop sending the handover command to the terminal device to save the base station resource. The maximum number of handover command retransmissions can be manually set, or can be specified by a protocol, for example, it can be 2 times, or it can be other values.

Optionally, in order to detect the Preamble sent by the terminal device, the first access network device needs to perform a corresponding operation.

For example, after the first access network device determines that the terminal device is to be switched from the first cell to the second cell, the first access network device can obtain the identifier of the terminal device and the access parameter.

The identifier of the terminal device may include, for example, a Cell Radio Network Temming Identity (CRNTI) of the terminal device.

The access parameters of the terminal device may include, for example, a root sequence number (rootSequenceIndex), a zero correlation sequence configuration (zeroCorrelationZoneConfig), and a high speed flag (highSpeedFlag), and may of course include other parameters. Where rootSequenceIndex is used to generate the ZC of the Preamble The root set, rootSequenceIndex, is the ZC root with the smallest logical number in this ZC root set. By cyclically shifting each ZC root in the ZC root packet set, a Preamble required for random access can be generated. zeroCorrelationZoneConfig is used for the zero correlation window of Preamble detection. The cyclic shift length (Ncs) indirectly determines the amount of cyclic shift and the number of Preambles that can be generated by each ZC root, where Ncs is related to the cell radius. highSpeedFlag is used to indicate the calculation method corresponding to the cyclic shift amount.

Optionally, the identifier and the access parameter of the terminal device may be obtained from a second access network device where the target cell (ie, the second cell) to which the terminal device is to be switched. If the terminal device performs the handover without crossing the access network device, that is, the first access network device and the second access network device are the same access network device, then the first access network device (ie, the second access network) The device may directly allocate the identifier and the access parameter to the terminal device. If the terminal device performs the handover of the access network device, the first access network device and the second access network device are different access network devices. Then, the first access network device needs to obtain the identifier and access parameters of the terminal device from the second access network device. In this case, there are two possible acquisition methods:

The first mode: the first access network device and the second access network device have an X2 connection, and the first access network device can directly obtain the identifier of the terminal device from the second access network device by using the X2 connection. Access parameters.

The second mode: the first access network device does not have an X2 connection between the second access network device, and the first access network device can obtain the identifier of the terminal device from the second access network device by using the core network device. Access parameters.

After the first access network device obtains the identifier and the access parameter of the terminal device, the first access network device may calculate an identifier (Identify, ID) of the Preamble sent by the terminal device. There are 64 kinds of Preambles in LTE, and a maximum of 64 Preambles are allocated to a cell. When a terminal device performs cell access, the base station where the cell to be accessed is assigned a Preamble ID to the terminal device, and the terminal device is ready to connect. The base station where the incoming cell is located transmits the Preamble indicated by the ID of the Preamble. When the base station allocates the ID of the Preamble to the terminal device, it allocates according to the identifier of the terminal device, the access parameter, and the like. Therefore, in the embodiment of the present invention, the original serving cell of the terminal device The access network device (ie, the first access network device) may also calculate the ID of the Preamble according to the identifier of the terminal device and the access parameter, and the calculated ID is the same ID as the ID of the Preamble sent by the terminal device. In this way, the first access network device can detect whether the terminal device sends the Preamble to the second access network device.

Optionally, when the first access network device detects the Preamble, multiple Preambles may be detected, and the Preambles may be sent by different terminal devices. In the embodiment of the present invention, the first access network device has calculated the ID of the Preamble sent by the terminal device to be switched. Therefore, after detecting the Preamble, the first access network device may separately detect the ID of the detected Preamble. Matching with the calculated ID of the Preamble sent by the terminal device (the matching process is to perform a zero correlation operation, and the Preamble with the largest correlation value is regarded as the detected Preamble), if the detected Preamble ID and the calculated terminal device If the ID of the transmitted Preamble is successfully matched, the first access network device determines that the terminal device sends the Preamble to the second access network device through the second cell.

The number of the Preambles detected by the first access network device may be multiple, and the ID of the detected Preamble is successfully matched with the calculated ID of the Preamble sent by the terminal device, which may be that the detected Preamble has at least one Preamble ID. The matching of the calculated ID of the Preamble sent by the terminal device is successful.

The device in the embodiment of the present invention is described below with reference to the accompanying drawings.

Referring to FIG. 3, based on the same inventive concept, an embodiment of the present invention provides an access network device, which may include a memory 301, a processor 302, a transmitter 303, and a receiver 304.

The processor 302 may be a central processing unit (CPU) or an application specific integrated circuit (ASIC), and may be one or more integrated circuits for controlling program execution, and may be a field programmable gate array. The hardware circuit developed by Field Programmable Gate Array (FPGA) can be a baseband chip.

The number of memories 301 may be one or more. The memory 301 may include a read only memory (ROM), a random access memory (RAM), and a disk storage.

The transmitter 303 and the receiver 304 may belong to a radio frequency system for performing network communication with an external device such as a terminal device, and may specifically communicate with an external device through a network such as an Ethernet, a radio access network, or a wireless local area network. The sender 303 and the receiver 304 may be located in the same physical module, for example, in a physical module capable of implementing a transceiving function, such as the physical module may be referred to as a transceiver, or the transmitter 303 and the receiver 304 may also be located in separate entities. In the module.

The memory 301, the transmitter 303, and the receiver 304 may be connected to the processor 302 via a bus (as shown in FIG. 3 as an example), or may be separately connected to the processor 302 through a dedicated connection line.

By programming the processor 302, the code corresponding to the method shown above is solidified into the chip, so that the chip can perform the method shown in FIG. 2 during operation. How to design and program the processor 302 is a technique known to those skilled in the art, and details are not described herein.

The access network device may be configured to perform the method described in FIG. 2 above, for example, may be the first access network device as described above, and therefore, for functions implemented by each unit in the access network device, Please refer to the description of the previous method section for details.

Referring to FIG. 4, based on the same inventive concept, an embodiment of the present invention provides another access network device, where the access network device may include a sending module 401, a processing module 402, and a receiving module 403.

In an actual application, the physical device corresponding to the processing module 402 may be the processor 302 in FIG. 3, the physical device corresponding to the sending module 401 may be the transmitter 303 in FIG. 3, and the physical device corresponding to the receiving module 403 may be FIG. Receiver 304 in the middle.

In the embodiment of the present invention, if the first access network device does not receive the feedback of the terminal device for the handover command, it may determine whether the terminal device has received the device by detecting whether the terminal device has sent the Preamble to the second access network device. If the switching command sent by the first access network device detects that the terminal device sends the Preamble, the retransmission switching command can be stopped, so that the redundancy retransmission of the handover command can be effectively avoided, and the BLER indicator is prevented from being deteriorated if not detected. When the terminal device sends the Preamble, the first access network device can resend the switching command to ensure that the terminal device can A handover command is received to perform cell handover, and the handover success rate is improved.

In the present invention, it should be understood that the disclosed apparatus and method can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the unit or unit is only a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be used. Combinations can be integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be electrical or otherwise.

The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to implement the embodiments of the present invention.

The functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may also be an independent physical module.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a standalone product, may be stored in a computer readable storage medium. Based on such understanding, all or part of the technical solution of the present invention may be embodied in the form of a software product stored in a storage medium, including a plurality of instructions for causing a computer device (which may be a personal computer, A server, or network device, or the like, or a processor, performs all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: a universal serial bus flash drive, a removable hard disk, a ROM, a RAM, a magnetic disk, or an optical disk, and the like, which can store program codes.

The above embodiments are only used to describe the technical solutions of the present invention in detail, but the description of the above embodiments is only for the purpose of facilitating the understanding of the embodiments of the present invention, and should not be construed as limiting the embodiments of the present invention. Variations or substitutions that may be readily conceived by those skilled in the art are intended to be included within the scope of the present invention.

Claims

A cell switching method, comprising:

Determining, by the first access network device, that the terminal device residing in the first cell of the first access network device is about to switch to the second cell in the second access network device;

The first access network device sends a handover command to the terminal device, where the handover command is used to instruct the terminal device to switch to the second cell;

If the first access network device does not receive the feedback from the terminal device for the handover command, the first access network device detects whether the terminal device passes the second cell to the second connection The network access device sends a preamble sequence;

If the first access network device detects that the terminal device has sent the preamble sequence to the second access network device by using the second cell, the first access network device stops to the terminal The device resends the switching command.
The method of claim 1, wherein the method further comprises:

If the first access network device does not detect that the terminal device sends the preamble sequence to the second access network device by using the second cell, the first access network device re-directs to the terminal The device sends the switching command.
The method according to claim 1 or 2, wherein the first access network device determines that the terminal device residing in the first cell of the first access network device is about to switch to the second access network After the second cell in the device, the method further includes:

The access network device acquires an identifier and an access parameter of the terminal device.
The method of claim 3, wherein the method further comprises:

The first access network device calculates an identifier of the preamble sequence sent by the terminal device according to the identifier and the access parameter of the terminal device.
The method according to claim 4, wherein the detecting, by the first access network device, whether the terminal device sends a preamble sequence to the second access network device by using the second cell, includes:

The first access network device matches the identifier of the detected preamble sequence with the calculated identifier of the preamble sequence sent by the terminal device;

If the identifier of the detected preamble sequence matches the calculated identifier of the preamble sequence sent by the terminal device, the first access network device determines that the terminal device passes the second cell to the second interface. The network access device sends the preamble sequence.
An access network device, comprising:

a processing module, configured to determine that a terminal device that resides in a first cell of the access network device is about to switch to a second cell in the second access network device;

a sending module, configured to send a handover command to the terminal device, where the handover command is used to instruct the terminal device to switch to the second cell;

The processing module is further configured to: if the receiving module of the access network device does not receive the feedback of the terminal device for the handover command, detecting whether the terminal device passes the second cell to the second The access network device sends a preamble sequence;

The sending module is further configured to stop resending to the terminal device if the processing module detects that the terminal device has sent the preamble sequence to the second access network device by using the second cell The switching command.
The access network device according to claim 6, wherein the sending module is further configured to:

And if the processing module does not detect that the terminal device sends the preamble sequence to the second access network device by using the second cell, retransmitting the handover command to the terminal device.
The access network device according to claim 6 or 7, wherein the processing module is further configured to:

After determining that the terminal device residing in the first cell of the access network device is about to switch to the second cell in the second access network device, the identifier and the access parameter of the terminal device are obtained.
The access network device according to claim 8, wherein the processing module is further configured to:

And determining, according to the identifier and the access parameter of the terminal device, an identifier of the preamble sequence sent by the terminal device.
The access network device according to claim 9, wherein the processing module is configured to:

And matching the identifiers of the detected preamble sequences with the calculated identifiers of the preamble sequences sent by the terminal device;

If the identifier of the detected preamble sequence is successfully matched with the calculated identifier of the preamble sequence sent by the terminal device, determining that the terminal device sends the preamble to the second access network device by using the second cell sequence.
An access network device, comprising:

a memory for storing instructions;

a processor for executing the instructions stored by the memory:

Determining that the terminal device residing in the first cell of the access network device is about to switch to the second cell in the second access network device;

Transmitting, by the sender, a handover command to the terminal device, where the handover command is used to indicate that the terminal device switches to the second cell;

If the receiver does not receive the feedback of the terminal device for the handover command, detecting whether the terminal device sends a preamble sequence to the second access network device by using the second cell;

If it is detected that the terminal device has sent the preamble sequence to the second access network device by using the second cell, the transmitter stops the retransmission of the handover command to the terminal device.
The access network device according to claim 11, wherein the processor is further configured to:

If it is not detected that the terminal device sends the preamble sequence to the second access network device by using the second cell, the handover command is resent to the terminal device by using the transmitter.
The access network device according to claim 11 or 12, wherein the processor is further configured to:

After determining that the terminal device residing in the first cell of the access network device is about to switch to the second cell in the second access network device, the identifier and the access parameter of the terminal device are obtained.
The access network device according to claim 13, wherein the processor is further configured to:

And determining, according to the identifier and the access parameter of the terminal device, an identifier of the preamble sequence sent by the terminal device.
The access network device of claim 14, wherein the processor is configured to:

And matching the identifiers of the detected preamble sequences with the calculated identifiers of the preamble sequences sent by the terminal device;

If the identifier of the detected preamble sequence is successfully matched with the calculated identifier of the preamble sequence sent by the terminal device, determining that the terminal device sends the preamble to the second access network device by using the second cell sequence.