CN115811766A

CN115811766A - Cell switching method and communication device

Info

Publication number: CN115811766A
Application number: CN202111082788.1A
Authority: CN
Inventors: 郑午阳; 耿婷婷
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2023-03-17
Also published as: WO2023040787A1

Abstract

The embodiment of the application provides a cell switching method and a communication device, and relates to the field of communication. The cell switching method comprises the following steps: the terminal equipment executes a switching process from a source cell to a first target cell, wherein the first target cell belongs to a candidate cell set; the terminal equipment determines that switching failure occurs in the switching process; the terminal equipment determines rollback indication information, wherein the rollback indication information at least indicates whether to rollback to a source cell when the switching fails; and when the fallback indication information indicates to fallback to the source cell when the handover fails, the terminal device executes a fallback operation to the source cell. In this embodiment, the fallback indication information indicates whether the terminal device is fallback to the source cell after the handover failure occurs in the handover process, so that the terminal device can execute the fallback operation based on the fallback indication information, thereby simplifying the operation of the terminal device and improving the handover efficiency.

Description

Cell switching method and communication device

Technical Field

The present application relates to the field of communications, and in particular, to a cell switching method and a communication apparatus.

Background

In a mobile communication system, a terminal device may need to perform a handover (handover) procedure due to factors such as mobility, so as to handover data transmission from a source cell to a target cell.

During handover, a handover failure may occur. At present, when the terminal equipment fails to switch, the target cell is reselected and the cell switching process is executed again, but the efficiency of the process is not high.

Disclosure of Invention

The embodiment of the present disclosure provides a cell switching scheme.

In a first aspect, a cell handover method is provided. The method comprises the following steps: the terminal equipment executes a switching process from a source cell to a first target cell, wherein the first target cell belongs to a candidate cell set; the terminal equipment determines that switching failure occurs in the switching process; the terminal equipment determines rollback indication information, wherein the rollback indication information at least indicates whether to rollback to a source cell when the switching fails; and when the fallback indication information indicates to fallback to the source cell when the handover fails, the terminal device executes a fallback operation to the source cell.

Therefore, in the embodiment of the disclosure, the rollback indication information indicates whether the terminal device is rolled back to the source cell after the handover failure occurs in the handover process, so that the terminal device can execute the rollback operation based on the rollback indication information, thereby simplifying the operation of the terminal device and improving the handover efficiency.

In some embodiments of the first aspect, further comprising: when the time elapsed from the initiation of the handover procedure reaches a first preset time period or when the number of times of handover failure occurrence reaches a number threshold, the terminal device performs a cell selection procedure.

In some embodiments of the first aspect, further comprising: when the elapsed time reaches a first preset time period or the number of times of occurrence of a specific event reaches a time threshold, the terminal equipment executes a cell selection process; the starting time of the first preset time period may be when the first handover configuration message is received, when the handover process is started to be executed, or when a handover failure occurs; wherein the specific event may be when a handover failure occurs, when a fallback occurs, when the fallback succeeds, or when a handover is triggered.

Therefore, the rollback is limited through the first preset time period or the time threshold, the complexity of the terminal equipment caused by infinite rollback is avoided, and the energy consumption of the terminal equipment is also avoided being overlarge.

In some embodiments of the first aspect, further comprising: and when determining that the rollback operation fails, the terminal equipment executes a cell selection process.

Therefore, the terminal equipment can execute the cell selection process after the rollback operation fails, so that the transmission interruption caused by the rollback failure of the terminal equipment is avoided, and the switching efficiency is improved.

In some embodiments of the first aspect, further comprising: when the fallback indication information indicates not to fallback to the source cell when the handover fails, the terminal device performs a cell selection procedure.

Therefore, the terminal equipment can execute the cell selection process based on the backspacing indication information, and avoids transmission interruption caused by switching failure. Through the cell selection process, a more appropriate cell can be found as soon as possible, so that the switching efficiency is ensured.

In some embodiments of the first aspect, the fallback indication information further indicates at least one of: a first preset time period or number threshold.

In some embodiments of the first aspect, further comprising: the terminal equipment sends a first message to the network equipment of the source cell, wherein the first message indicates at least one of the following: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells when the backoff is successful; a second duration between occurrence of a handover failure and success of fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of fallback failure; or a third duration from the occurrence of the handover failure to the fallback failure.

Therefore, when handover failure occurs, the terminal device can report information of various aspects of the handover failure to the network device of the source cell through the first message, so that the network device can more comprehensively know the handover process, and further optimization of mobility management is facilitated.

In some embodiments of the first aspect, further comprising: when the cell selection process selects a second target cell in the candidate cell set, the terminal device executes a handover process to the second target cell; when the cell selection process selects a second target cell which does not belong to the candidate cell set, the terminal equipment executes a Radio Resource Control (RRC) reestablishment process with the second target cell; or when the suitable cell cannot be found in the second preset time period, the terminal equipment is switched to an idle state.

In some embodiments of the first aspect, further comprising: when the cell selection process selects a second target cell, the terminal device executes an RRC reestablishment process with the second target cell; or when the suitable cell cannot be found in the second preset time period, the terminal equipment is switched to an idle state.

Therefore, a new cell can be determined through the cell selection process, and then cell switching and other operations are executed aiming at the new cell, so that the switching continuity of the terminal equipment is ensured, and the switching efficiency is improved.

In some embodiments of the first aspect, further comprising: when the cell selection process selects the second target cell and the handover to the second target cell is successful, the terminal device sends a second message indicating at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells in the candidate cell set when the fallback is successful; a second duration between the occurrence of the handover failure and the success of the fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of fallback failure; a third duration between occurrence of a handover failure and a fallback failure; a fourth duration from the failure to fallback to successful selection of the second target cell; or a fifth time period from the occurrence of the handover failure to the successful selection of the second target cell.

In this way, after the target cell for handover is successfully selected, the terminal device can report various information about the handover process to the network device of the source cell through the second message, so that the network device can more comprehensively understand the handover process, thereby facilitating further optimization of mobility management.

In some embodiments of the first aspect, the fallback indication information is received from a network device of the source cell, or wherein the fallback indication information is preconfigured in the terminal device.

In a second aspect, a method for cell handover is provided. The method comprises the following steps: the network equipment sends back indication information to the terminal equipment, wherein the back indication information at least indicates whether the terminal equipment backs to a source cell when the switching fails, and the network equipment is the network equipment of the source cell when the terminal equipment executes the switching process; and when the terminal equipment fails to switch in the switching process and the rollback indication information indicates that the terminal equipment backs to the source cell when the terminal equipment fails to switch, the network equipment executes the operation of connecting with the terminal equipment based on the rollback operation of the terminal equipment.

In some embodiments of the second aspect, further comprising: the network equipment receives a switching report message from the terminal equipment, wherein the switching report message indicates at least one of the following: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell to which a handover procedure is handed over when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells when the backoff is successful; a second duration between occurrence of a handover failure and success of fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of fallback failure; a third duration between occurrence of a handover failure and a fallback failure; a fourth time period from the fallback failure to the successful selection of the camped cell; or a fifth time period from the occurrence of a handover failure to the successful selection of the camped cell.

In a third aspect, a communications apparatus is provided. The communication device includes: a handover module configured to perform a handover procedure from a source cell to a first target cell, the first target cell belonging to a set of candidate cells; a first determination module configured to determine that a handover failure occurs in a handover procedure; a second determining module configured to determine fallback indication information indicating at least whether to fallback to a source cell upon handover failure; and a fallback module configured to perform a fallback operation to the source cell when the fallback indication information indicates to fallback to the source cell upon handover failure. The communication device may be adapted to implement the method of the first aspect or any embodiment of the first aspect.

In a fourth aspect, a communication device is provided. The communication device includes: a sending module configured to send fallback indication information to the terminal device, where the fallback indication information at least indicates whether to fallback to a source cell when handover fails, and the communication device is a network device of the source cell when the terminal device executes a handover procedure; and a connection module configured to execute an operation of connecting with the terminal device based on a fallback operation of the terminal device when the terminal device has a handover failure in a handover procedure and the fallback indication information indicates to fallback to the source cell at the time of the handover failure. The communication device may be adapted to implement the method of the second aspect or any embodiment of the second aspect.

In a fifth aspect, a terminal device is provided. The terminal device comprises a processor and a memory having stored thereon instructions for execution by the processor, which when executed by the processor, cause the terminal device to: performing a handover procedure from a source cell to a first target cell, the first target cell belonging to a set of candidate cells; determining that a handover failure occurs in a handover process; determining fallback indication information, wherein the fallback indication information at least indicates whether to fallback to a source cell when handover fails; and performing a fallback operation to the source cell when the fallback indication information indicates to fallback to the source cell upon handover failure.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: the cell selection process is performed when an elapsed time from initiation of the handover process reaches a first preset time period or when the number of times of occurrence of handover failure reaches a number threshold.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: when the elapsed time reaches a first preset time period or the number of times of occurrence of a specific event reaches a time threshold, executing a cell selection process; the starting time of the first preset time period may be when the first handover configuration message is received, when the handover process is started to be executed, or when handover failure occurs; wherein the specific event may be when a handover failure occurs, when a fallback occurs, when the fallback succeeds, or when a handover is triggered.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: when it is determined that the fallback operation fails, a cell selection procedure is performed.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: when the fallback indication information indicates not to fallback to the source cell upon handover failure, a cell selection procedure is performed.

In some embodiments of the fifth aspect, the fallback indication information further indicates at least one of: a first predetermined time period or number threshold.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: transmitting, via the transceiver, a first message to a network device of the source cell, the first message indicating at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells when the backoff is successful; a second duration between the occurrence of the handover failure and the success of the fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of failure of the fallback; or a third duration from the occurrence of the handover failure to the fallback failure.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: performing a handover procedure to a second target cell in the candidate cell set when the cell selection procedure selects the second target cell; when the cell selection process selects a second target cell which does not belong to the candidate cell set, performing a Radio Resource Control (RRC) reestablishment process with the second target cell; or when a suitable cell cannot be found within a second preset time period, the idle state is switched to.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: when the cell selection process selects a second target cell, performing an RRC reestablishment process with the second target cell; or when a suitable cell cannot be found within a second preset time period, the idle state is switched to.

In some embodiments of the fifth aspect, execution of the instructions by the processor causes the terminal device to: sending, via the transceiver, a second message when the cell selection procedure selects the second target cell and successfully hands over to the second target cell, the second message indicating at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells in the candidate cell set when the fallback is successful; a second duration between occurrence of a handover failure and success of fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of fallback failure; a third duration between occurrence of a handover failure and a fallback failure; a fourth duration from the failure to fallback to successful selection of the second target cell; or a fifth time period from the occurrence of the handover failure to the successful selection of the second target cell.

In some embodiments of the fifth aspect, the fallback indication information is received from a network device of the source cell, or wherein the fallback indication information is preconfigured in the terminal device.

In a sixth aspect, a network device is provided. The network device includes a processor and a memory having stored thereon instructions for execution by the processor, which when executed by the processor, cause the network device to: the method comprises the steps that backspacing indication information is sent to terminal equipment through a transceiver, the backspacing indication information at least indicates whether the terminal equipment backs to a source cell when switching fails, and the network equipment is network equipment of the source cell when the terminal equipment executes a switching process; and when the terminal equipment fails to switch in the switching process and the rollback indication information indicates to roll back to the source cell when the switching fails, executing the operation of connecting with the terminal equipment based on the rollback operation of the terminal equipment.

In some embodiments of the sixth aspect, execution of the instructions by the processor causes the network device to implement: receiving, via the transceiver, a handover report message from the terminal device, the handover report message indicating at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell to which a handover procedure is handed over when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells when the fallback is successful; a second duration between occurrence of a handover failure and success of fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of failure of the fallback; a third duration between occurrence of a handover failure and a fallback failure; a fourth duration from the failure of fallback to the successful selection of the camped cell; or a fifth time period from the occurrence of a handover failure to the successful selection of the camped cell.

In a seventh aspect, there is provided a computer-readable storage medium having stored thereon computer-executable instructions that, when executed by a processor, perform operations in accordance with the method of the first aspect or any embodiment thereof above, or in accordance with the method of the second aspect or any embodiment thereof above.

In an eighth aspect, a chip or chip system is provided. The chip or system of chips comprises processing circuitry configured to perform operations according to the method of the above first aspect or any embodiment thereof, or to perform operations according to the method of the above second aspect or any embodiment thereof.

In a ninth aspect, a computer program or computer program product is provided. The computer program or computer program product is tangibly stored on a computer-readable medium and comprises computer-executable instructions that, when executed, implement operations according to the method of the first aspect or any embodiment thereof described above, or implement operations according to the method of the second aspect or any embodiment thereof described above.

Drawings

Fig. 1 shows an interactive signaling diagram of a conventional handover procedure of a terminal device from a source cell to a target cell;

FIG. 2 illustrates a schematic diagram of a communication system in which embodiments of the present disclosure may be implemented;

figure 3 illustrates an interactive signaling diagram of a handover procedure for a terminal device successfully handing over from a source cell to a target cell, in accordance with some embodiments of the present disclosure;

figure 4 shows a schematic flow diagram of a process for a terminal device to perform a cell handover in accordance with some embodiments of the present disclosure;

figure 5 shows a schematic flow diagram of a process performed by a terminal device after a handover failure has occurred in accordance with some embodiments of the present disclosure;

figure 6 shows a schematic flow diagram of a process for cell handover in accordance with some embodiments of the present disclosure;

fig. 7 shows a schematic block diagram of a communication device for cell handover in accordance with some embodiments of the present disclosure;

fig. 8 illustrates another schematic block diagram of a communication apparatus for cell handover in accordance with some embodiments of the present disclosure; and

FIG. 9 illustrates a schematic block diagram of an example device that can be used to implement embodiments of the present disclosure.

Detailed Description

Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure are shown in the drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the disclosure are for illustration purposes only and are not intended to limit the scope of the disclosure.

In describing embodiments of the present disclosure, the terms "include" and "comprise," and similar language, are to be construed as open-ended, i.e., "including but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first," "second," and the like may refer to different or the same object. Other explicit and implicit definitions are also possible below.

Embodiments of the present disclosure may be implemented in accordance with suitable communication protocols, including, but not limited to, third generation (3 rd generation, 3G), fourth generation (4G), fifth generation (5G), and like cellular communication protocols, wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and like wireless local area network communication protocols, future evolution mobile communication systems such as 6G communication system protocols, and/or other protocols now known or later developed.

The technical solution of the embodiments of the present disclosure is applied to a communication system following any appropriate communication protocol, for example: universal Mobile Telecommunications System (UMTS), long Term Evolution (LTE) system, wideband Code Division Multiple Access (WCDMA), code Division Multiple Access 2000 system (Code Division Multiple Access, CDMA 2000), time Division-synchronous Code Division Multiple Access (TD-SCDMA), frequency Division Duplex (FDD), time Division Duplex (TDD), fifth generation (5G) or New Radio (New Radio, NR), future Evolution 6G communication system, etc.

For purposes of illustration, embodiments of the present disclosure are described below in the context of NR communication systems in 3 GPP. However, it should be understood that embodiments of the present disclosure are not limited to this communication system, but may be applied to any communication system in which similar problems exist, such as a Wireless Local Area Network (WLAN), a wired communication system, or other communication systems developed in the future, and the like.

The term "terminal device" as used in this disclosure refers to any terminal device capable of wired or wireless communication with network devices or with each other. A terminal device may sometimes be referred to as a User Equipment (UE). The terminal device may be any type of mobile terminal, fixed terminal or portable terminal. As an example, the Terminal device may include a Mobile handset, a station, a unit, a device, a Mobile Terminal (MT), a subscription station, a portable subscription station, an Internet node, a communicator, a desktop computer, a laptop computer, a notebook computer, a tablet computer, a Personal communication system device, a Personal navigation device, a Personal Digital Assistant (PDA), a positioning device, a radio broadcast receiver, an electronic book device, a gaming device, an Internet of Things (IoT) device, a vehicle device, an aircraft, a Virtual Reality (VR) device, an Augmented Reality (AR) device, a wearable device, a Terminal device in a 5G Network or any Terminal device in an evolved Public Land Mobile Network (PLMN), other devices that may be used for communication, or any combination thereof. The embodiments of the present disclosure do not limit this.

The term "network device" as used in this disclosure is an entity or node that may be used to communicate with a terminal device, which may be an access network device, for example. The Access Network device may be a device deployed in a Radio Access Network to provide a wireless communication function for the mobile terminal, and may be, for example, a Radio Access Network (RAN) Network device. The access network equipment may include various types of base stations. By way of example, access network equipment may include various forms of macro base stations, micro base stations, pico base stations, femto base stations, relay stations, access points, remote Radio Units (RRUs), radio Heads (RH), remote Radio Heads (RRHs), and so on. In systems using different radio access technologies, names of access network devices may be different, for example, referred to as evolved node B (evolved NodeB, eNB or eNodeB) in a Long Term Evolution (LTE) network, referred to as node B (NodeB, NB) in a 3G network, referred to as G node B (gNB) or NR node B (NR NB) in a 5G network, and so on. In some scenarios, an access network device may include a Central Unit (CU) and/or a Distributed Unit (DU). CUs and DUs can be placed in different places, for example: and the DU is pulled away and is placed in an area with high telephone traffic, and the CU is placed in a central computer room. Alternatively, CU and DU may be located in the same room. CU and DU can also be different components under one chassis. For convenience of description, in the embodiments that follow in the present disclosure, the above-mentioned apparatuses for providing a mobile terminal with a wireless communication function are collectively referred to as network devices, and the embodiments of the present disclosure are not limited in detail.

Fig. 1 shows an interactive signaling diagram of a conventional handover procedure 100 for a terminal device to handover from a source cell to a target cell. In fig. 1, a terminal 101, a network 102 of a source cell and a network 103 of a target cell are involved.

In process 100, network device 102 of the source cell sends 110 a handover request to network device 103 of the target cell. Specifically, the handover is initiated by the source cell, and the network device 102 of the source cell may send a handover request via an Xn interface between the network device 102 of the source cell and the network device 103 of the target cell. The handover request may include at least an identification of the terminal device 101.

The network device 103 of the target cell performs 120 Admission control (Admission control). Specifically, the network device 103 of the target cell may determine Radio Resource Control (RRC) reconfiguration information required by the terminal device 101 to perform handover based on the handover request. The RRC reconfiguration information may include a cell identity of the target cell and access information required for terminal device 101 to access the target cell.

The network device 103 of the target cell sends 130 a handover request confirm message to the network device 102 of the source cell, the handover request confirm message comprising RRC reconfiguration information.

The network device 102 of the source cell sends 140 a handover message to the terminal device 101, the handover message comprising RRC reconfiguration information. Specifically, after receiving the handover request confirm message, the network device 102 of the source cell may extract the RRC reconfiguration information therefrom and forward the RRC reconfiguration information to the terminal device 101 through the handover message. In a communication system such as LTE, the handover message may carry RRC reconfiguration information through a mobile control information (MobilityControlInfo) information element. In a communication system such as NR, the handover message may carry RRC reconfiguration information through a reconfiguration with synchronization (reconfiguration within sync) cell.

Terminal device 101 switches 150 to the target cell based on the RRC reconfiguration information. Specifically, the terminal apparatus 101 may access the target cell based on the RRC reconfiguration information without acquiring system information from the network apparatus 103 of the target cell. Subsequently, the terminal device 101 sends 160 an RRC reconfiguration complete message to the network device 103 of the target cell.

Thus, with process 100, a handover process of terminal device 101 from a source cell to a target cell may be achieved. However, in process 100, as network device 102 of the source cell sends a handover message (i.e., 140 in fig. 1) to terminal device 101, data transmission between network device 102 of the source cell and terminal device 101 is also interrupted. After the terminal device 101 sends an RRC reconfiguration complete message (i.e. 160 in fig. 1) to the network device 103 of the target cell, the network device 103 of the target cell starts data transmission with the terminal device 101. It can be seen that there is an interruption delay in the handover process as shown in fig. 1. In addition, if a handover failure occurs in the process 100 as in fig. 1, the terminal apparatus 101 needs to re-perform cell selection, which results in inefficient handover.

In view of this, embodiments of the present disclosure provide a cell handover scheme. Particularly, when cell handover failure occurs, whether to fallback to a source cell can be determined based on the fallback indication information, so that handover efficiency can be improved.

Fig. 2 illustrates a schematic diagram of a communication system 200 in which embodiments of the present disclosure may be implemented. The system 200 shown in fig. 2 includes a terminal device 210, the terminal device 210 is located in a cell 222, and a network device of the cell 222 is a network device 232. Also shown in fig. 2 are cell 224 and cell 226, and network device 234 of cell 224 and network device 236 of cell 226.

The terminal device 210 is capable of communicating with the network device 232. In some scenarios, the terminal device 210 may reach the edge of the cell 222, or the signal quality between the network device 232 and the terminal device 210 may deteriorate, due to factors such as movement of the terminal device 210, thereby triggering a cell handover procedure. In a cell handover scenario, a cell 222 in which the terminal device 210 is currently located may be referred to as a source cell, and accordingly, the network device 232 of the cell 222 may be referred to as a source network device. Cell 224 may be referred to as a first target cell and network device 234 may accordingly be referred to as a first target network device. Similarly, cell 226 may be referred to as a second target cell and network device 236 may be referred to as a second target network device accordingly. Or alternatively, cell 224 and cell 226 may be collectively referred to as candidate (candidate) cells.

It is to be understood that fig. 2 is merely an illustration, and although fig. 2 shows two target cells, namely cell 224 and cell 226, embodiments of the present disclosure do not limit the number of target cells, etc. In addition, it should be further understood that the terms of the source cell, the candidate cell, the target cell, and the like are only schematic, and the terms may be changed for different terminal devices or different handover scenarios, and are not described herein again.

Some embodiments of the present disclosure will be described below in conjunction with the communication system 200 shown in fig. 2.

Fig. 3 illustrates an interactive signaling diagram of a handover procedure 300 for a terminal device successfully handing over from a source cell to a target cell in accordance with some embodiments of the present disclosure. As illustrated, the process 300 involves the terminal device 210, the source network device 232, the first target network device 234, and the second target network device 236. That is, the process 300 is described by taking the handover process of the terminal device 210 as an example, and it can be understood that the process is also applicable to handover of other terminal devices, and is not described herein again.

The source network device 232 sends 302 measurement configuration information to the terminal device 210. The terminal device 210 performs 304 measurements based on the measurement configuration information, and the terminal device 210 sends 306 a measurement report to the source network device 232. Specifically, the terminal device 210 may periodically perform measurements and periodically transmit measurement reports accordingly. The measurement report may include measurement results of various cells (such as cell 222, cell 224, and cell 226) measured by the terminal device 210, for example, at least one of the following: signal to Interference plus Noise Ratio (SINR), received Signal Strength (RSSI), reference Signal Received Power (RSRP), reference Signal Received Quality (RSRQ), and the like.

The source network device 232 determines 308 a handover type. The Handover type in the embodiment of the present disclosure may be a hybrid Handover type, or may also be referred to as a Dual Active Protocol Stack (DAPS) Handover and Conditional Handover (CHO) composite type, which is abbreviated as DAPS + CHO. It should be noted, however, that the present disclosure is not so limited, e.g., the handover type may be a DAPS handover, or the handover type may be a CHO, or the handover type may be another type, which is not listed here.

The source network device 232 sends 310 a handover request to the network device of each candidate cell in the set of candidate cells. Specifically, the source network device 232 sends 3102 a first handover request to the first target network device 234 and sends 3104 a second handover request to the second target network device 236.

It is understood that at least one candidate cell is included in the candidate cell set, which may be determined by the source network device 232 based on the measurement report, and that the number of at least one candidate cell is determined based on the actual situation, which may be 1 or 2 or more, for example. And it should be understood that although embodiments herein show the candidate set of cells including the first target cell 224 and the second target cell 226, the disclosure is not so limited.

The network device 234/236 of the at least one candidate cell performs 312 admission control (admission control). Specifically, the first target network device 234 performs 3122 admission control and the second target network 236 performs 3124 admission control.

The network device 234/236 of the at least one candidate cell sends 314 a handover request confirm message to the source network device 232. In particular, the first target network device 234 sends 3142 a first handover request confirm message to the source network device 232, which may include first configuration information of the first target network device 234. The second target network device 236 sends 3144 a second handover request confirm message, which may include second configuration information of the second target network device 236, to the source network device 232.

The source network device 232 sends 316 an RRC reconfiguration message to the terminal device 210, which may include handover configuration information and handover conditions of at least one candidate cell (cell 224 and cell 226).

Illustratively, the source network device 232 may send the RRC reconfiguration message when the link quality between the source network device 232 and the terminal device 210 is higher than a certain set threshold, which can ensure that the terminal device 210 successfully receives the RRC reconfiguration message. The handover configuration information of the candidate Cell may include an Identifier of the candidate Cell and frequency information corresponding to the candidate Cell, where the Identifier may be a Cell Global Identifier (CGI) or a Physical Cell Identifier (PCI), and the like. Additionally or alternatively, the handover configuration information of the candidate cell may include DAPS configuration information of the candidate cell. The DAPS configuration information may include indication information of a Data Radio Bearer (DRB) supporting the DAPS, and/or may include power information between two network devices when the DAPS is used.

Additionally or alternatively, the source network device 232 may further send fallback indication information to the terminal device 210, for indicating whether the terminal device 210 performs a fallback operation when a handover failure occurs. The fallback indication information may be included in the RRC reconfiguration message or the fallback indication information may be included in another message. Embodiments related to the fallback indication information may refer to the parts described below in connection with fig. 4 and 5. In the embodiment of the present application, fallback (fallback) may refer to a procedure that the terminal device 210 reestablishes the RRC connection with the source network device 232 when the terminal device 210 fails to perform handover (e.g., DAPS HO, CHO, or DAPS + CHO).

Additionally or alternatively, the source network device 232 may also send other reconfiguration messages to the terminal device 210 to inform the terminal device 210 of handover configuration information of at least one candidate cell.

The terminal device 210 sends 318 an RRC reconfiguration complete message to the source network device 232.

It should be understood that the period of 302 to 318 in fig. 3 may be referred to as a handover preparation (HO preparation) period. Taking Downlink (DL) data transmission as an example, during handover preparation, a forwarding path (forwarding tunnel) has been established, specifically, a forwarding path from the source network device 232 to the first target network device 234 and a forwarding path from the source network device 232 to the second target network device 236 are established.

Additionally or alternatively, if EARLY data forwarding is applied, the source network device 232 sends 320 an EARLY STATUS TRANSFER (EARLY STATUS TRANSFER) message to the first target network device 234 and the second target network device 236. Optionally, early data forwarding may also be triggered. Taking DL data transmission as an example, the source network device 232 may forward the downstream data to the first target network device 234 and the second target network device 236.

It is understood that, taking downlink Data transmission as an example, the source network device 232 is responsible for allocating downlink Packet Data Convergence Protocol (PDCP) Sequence Numbers (SNs) until the SN allocation is handed off to the first target network device 234. That is, the source network device 232 will not stop allocating downlink PDCP SNs until it receives a handover success message (330, below) from the first target network device 234.

The terminal device 210 evaluates 322 the handover condition. Specifically, the terminal device 210 maintains the connection with the source network device 232 after receiving the handover configuration information, and the terminal device 210 starts evaluating handover conditions for at least one candidate cell.

The terminal device 210 selects 324 the target cell. Specifically, the terminal device 210 may determine whether there is a candidate cell satisfying the handover condition by evaluating the handover condition. The terminal device 210 may select a target cell if there are candidate cells satisfying the handover condition. In fig. 3, it is assumed that the terminal device 210 has selected the first target cell 224, wherein the first target cell 224 belongs to the candidate cell set.

The terminal device 210 switches 326 to the first target cell 224. Specifically, terminal device 210 may handover to first target cell 224 based on previously acquired handover configuration information for first target cell 224.

The terminal device 210 sends 328 an RRC reconfiguration complete message to the first target network device 234.

It should be understood that the period of 320 to 328 in fig. 3 may be referred to as a handover execution (HO execution) period. The period of 329 to 334 in fig. 3 may be referred to as a handover Completion (HO Completion) period.

After the handover execution period, the terminal device 210 detaches (detach) 329 from the source cell 222. That is, the terminal device 210 may release the connection with the source cell 222.

The first target network device 234 sends 330 a handover success message to the source network device 232. The handover success message is used to inform the source network device 232 that the terminal device 210 has successfully accessed the first target network device 234. Thus, the source network device 232 stops data transmission with the terminal device 210.

The source network device 232 sends 332 a SN status transfer message to the first target network device 234, which may include the last data transmission sequence number assigned by the source network device 232. Optionally, the source network device 234 may also initiate late-stage data forwarding.

The source network device 232 sends 334 a handover cancel message to the second target network device 236.

In this way, the terminal device 210 can successfully handover from the source cell 222 to the first target cell 224 through the handover procedure 300 as shown in fig. 3.

The process achieves cell handover enhancement, and 0 millisecond (or close to 0 millisecond) interrupt delay is achieved in the handover process. Specifically, during the handover procedure, the source network device 232 sends PDCP SDUs associated with the PDCP SNs to the first target network device 234, such that the first target network device 234 also performs header compression, ciphering, and the like on the PDCP SDUs. Taking downlink transmission as an example, in the handover process, data transmission between the source network device 232 and the terminal device 210 is not interrupted, and both the first target network device 234 and the source network device 232 send downlink data to the terminal device 210, thereby shortening the interruption time of data transmission. In the process that the terminal device 210 performs data communication with the source network device 232 and the first target network device 234 at the same time, the terminal device 210 has two sets of protocol stacks, which are called DAPS, and correspond to the data communication of the source network device 232 and the first target network device 234, respectively. In an actual scenario, some Data Radio Bearers (DRBs) may support the DAPS, and other DRBs do not need to perform the DAPS processing, so that the resource utilization rate can be improved.

In addition, in the handover procedure 100 shown in fig. 1, mobility management of the terminal device 101 in the RRC connected state is controlled by the network device 102 of the source cell. Specifically, the network device 102 of the source cell sends a handover message to the terminal device 101 to instruct the terminal device 101 to which target cell the terminal device 101 is handed over to and how to perform the handover, and then the terminal device 101 may access the target cell based on the content contained in the received handover message. It can be seen that in the process 100 shown in fig. 1, the successful sending of the handover message is a necessary condition for ensuring a successful handover under the handover mechanism. However, in the LTE system or the NR system, fast attenuation of signal quality, fast movement of the terminal device, blocking of an object, and a long duration of handover preparation may cause a handover message transmission failure, which may further cause a handover failure and reduce a handover success rate. In addition, in the handover process 100 shown in fig. 1, the network device 102 of the source cell generally determines whether to instruct the terminal device 101 to perform handover based on the signal quality reported by the terminal device 101, for example, when the terminal device 101 detects that the signal quality of the neighboring cell is better than the signal quality of the current serving cell by a certain threshold, the terminal device 101 reports the measurement result. However, in the LTE system or the NR system, rapid attenuation of signal quality, rapid movement of the terminal device, blocking of an object, a long duration of handover preparation, and the like may cause a failure in sending a measurement report, and further may cause a handover failure, thereby reducing a handover success rate.

Unlike the process 100 in fig. 1, the handover process 300 shown in fig. 3 is decided and triggered by the terminal device 210, as depicted by 322-328, and the handover process between 322-328 in fig. 3 is insensitive to the source network device 232. Therefore, the change of the environment where the terminal device 210 is located can be fully considered, the terminal device 210 triggers the switching, and the success rate of the switching can be improved.

As described above, the handover procedure 300 shown in fig. 3 has a DAPS + CHO composite handover type, and can be triggered by the terminal device 210 and achieve a minimum interruption delay, thereby ensuring handover efficiency.

However, in the handover procedure with the handover type DAPS + CHO, a handover failure may occur. The following describes a processing scheme of handover failure in an embodiment of the present disclosure with reference to fig. 4 to 5.

Fig. 4 shows a schematic flow diagram of a process 400 for a terminal device to perform a cell handover in accordance with some embodiments of the present disclosure. Process 400 may be performed by terminal device 210.

At block 410, the terminal device 210 performs a handover procedure from the source cell 222 to a first target cell 224, wherein the first target cell 224 belongs to the candidate set of cells.

Alternatively, the handover procedure to the first target cell 224 may be performed with reference to 322 to 326 as shown in fig. 3. It is understood that embodiments of the present disclosure are not limited thereto, and other handover types or procedures, for example, may be employed to perform handover from the source cell 222 to the first target cell 224.

It is understood that prior to 410, the terminal device 210 may receive a first handover configuration message, e.g., an RRC reconfiguration message, from the source network device 232. The first handover configuration message may include a trigger condition, handover configuration information for each candidate cell in the set of candidate cells.

Additionally or alternatively, the first handover configuration message may further include fallback indication information for indicating whether the terminal device 210 reverts to the source cell when a handover failure occurs.

Additionally or alternatively, the first handover configuration message may further comprise a first preset time period or number threshold. The first preset time period or the number threshold may be used to indicate the timing of executing the backoff by the terminal device 210, and specifically, if the first preset time period is exceeded or the number of times of occurrence of a specific event reaches the number threshold, the backoff is not executed any more. In some embodiments, whether the first preset time period is reached may be determined by a first timer, wherein the starting (or resetting) time of the first timer may be any one of: when a first handover configuration message is received, when a handover procedure is started, or when a handover failure occurs, etc. In some embodiments, it may be determined by a counter whether a number threshold is reached, where the time of initiation (or reset) of the number threshold may be any of: when a handover failure occurs, when a fallback occurs, when the fallback succeeds, or when a handover is triggered, etc.

Additionally or alternatively, the first handover configuration message may further include a second preset time period. The second preset time period may be used to indicate the timing of cell selection by the terminal device 210, and specifically, if no suitable cell is found beyond the second preset time period, the cell selection is stopped and the idle state is entered. In some embodiments, it may be determined by a second timer whether a second preset time period is reached, wherein the starting time of the second timer may be any one of: when a first handover configuration message is received, when a handover procedure is started, when a handover failure occurs, when a fallback failure occurs, and the like.

Additionally or alternatively, the first handover configuration message may further include first indication information for indicating whether the terminal device 210 sends the first message to the source network device 232 when a handover failure occurs.

Additionally or alternatively, the first handover configuration message may also include an identification of the other cell for instructing the terminal device 210 to send a second message to the network device of the other cell after successful selection of the target cell, as described below in connection with 538.

Specifically, the terminal device 210 may determine the candidate cell satisfying the trigger condition as the first target cell 224 based on the first handover configuration message. The terminal device 210 may then perform a handover procedure based on the handover configuration information of the first target cell 224.

At block 420, the terminal device 210 determines that a handover failure occurred during the handover procedure.

Handover failure may occur for various reasons, such as premature timing of the handover, late timing of the handover, or selection of the wrong cell.

The Too Early time of the Handover may also be referred to as Too Early Handover (Too Early Handover), and Radio Link Failure (RLF) occurs between the terminal device and the target cell within a short time (for example, a preset time period) after the terminal device is successfully handed over from the source cell to the target cell, or the terminal device fails Handover during the Handover process, which may be because the connection quality between the terminal device and the network device of the target cell is poor and RLF is likely to occur due to the Too Early Handover process performed by the terminal device.

The Too Late Handover timing may also be referred to as Too Late Handover (Too Late Handover), where the terminal stays in the source cell for a long time before RLF occurs, but the Handover has not yet been started, possibly because the terminal performs the Handover procedure Too Late.

If a Wrong Cell or a Cell causing Handover (Handover to wlan Cell) is selected, the terminal device 210 may select a certain Cell (assumed as Cell a) as the target Cell, but actually may be Cell B, which may cause RLF to occur soon after the terminal device is handed over from the source Cell to Cell a, or cause Handover failure during Handover due to poor link quality between the network device of Cell a and the terminal device.

Additionally or alternatively, the terminal device 210 may further determine whether to send the first message to the source network device 232 based on the first indication information, where the first indication information is used to indicate whether to send the first message to the source network device when the handover failure occurs. Further, if the first indication information indicates that the first message is sent to the source network device when the handover failure occurs, the terminal device 210 may send the first message to the source network device 232. For this first message, reference may be made to the following detailed description in conjunction with 529 in fig. 5, and details are not repeated here for the sake of brevity.

At block 430, the terminal device 210 determines fallback indication information indicating at least whether to fallback to the source cell upon handover failure.

Specifically, the terminal device 210 may determine the previously stored fallback indication information, for example, locally obtain the fallback indication information from the terminal device 210.

In some embodiments, the fallback indication information may be sent by the source network device 232 to the terminal device 210.

In some examples, the source network device 232 may send the fallback indication information to the terminal device 210 via an RRC reconfiguration message (e.g., 316 in fig. 3), that is, the RRC reconfiguration message includes the fallback indication information. In connection with fig. 3, for example, the source network device 232 may send the fallback indication information to the first target network device 234, such as via the first handover request message at 3102 or via other signaling at other times, the first target network device 234 may include the fallback indication information in a first handover request confirm message and send 3142 to the source network device 232, such that the source network device 232 may send an RRC reconfiguration message including the fallback indication information to the terminal device 210 at 316. In connection with fig. 3, for example, after receiving 3142 the first handover request confirm message from the first target network device 234, the source network device 232 may add the fallback indication information thereto and send 316 an RRC reconfiguration message including the fallback indication information to the terminal device 210.

In some examples, the source network device 232 may send the fallback indication information to the terminal device 210 via another message than the RRC reconfiguration message (e.g., 316 in fig. 3). In conjunction with fig. 3, for example, the source network device 232 may send the fallback indication information to the terminal device 210 before 316 or after 316. In some examples, the source network device 232 may send the fallback indication information to the terminal device 210 in other manners. For example, the source network device 232 may send the fallback indication information through a system message (e.g., MIB, SIB1, etc.), an RRC configuration message, etc., which is not limited by the present disclosure. It can be understood that, the signaling carrying the fallback indication information is not limited in the embodiments of the disclosure, and may be, for example, RRC layer signaling, medium Access Control (MAC) signaling, or physical layer signaling.

In some embodiments, the fallback indication information may be pre-configured, e.g. pre-defined by a protocol, which may save signaling overhead.

In block 440, the terminal device 210 performs a fallback operation to the source cell 222 when the fallback indication information indicates fallback to the source cell upon handover failure.

Specifically, the terminal device performing the fallback operation may refer to the terminal device 210 fallback to (fallback to) the source cell configuration and restoring the connection with the source cell 222.

It can be understood that if no Radio Link Failure (RLF) occurs in the Link between the terminal device 210 and the source cell 222, the previous source cell configuration can be directly used to recover the connection without triggering the RRC connection re-establishment procedure. However, if the link between the terminal device 210 and the source cell 222 has been released, it may result in an inability to recover the connection, i.e. a fallback failure may occur. An example embodiment of the subsequent operation of the terminal device 210 based on the fallback indication information will be described below in conjunction with fig. 5. Fig. 5 shows a schematic flow diagram of a process 500 performed by a terminal device after a handover failure occurs, in accordance with some embodiments of the present disclosure.

At block 510, the terminal device 210 determines whether the fallback indication information indicates fallback to the source cell upon handover failure. If so, 520 is performed. If not, 530 is performed.

At block 520, the terminal device 210 determines whether a fallback condition is satisfied. If so, 522 is performed. If not, 530 is performed.

Illustratively, the fallback condition may include that the elapsed time is below a first preset time period or that the number of times a certain event occurs is below a number threshold. For example, the elapsed time being lower than the first preset time period may include any one of: the time elapsed since the reception of the first handover configuration message is lower than a first preset time period, the time elapsed since the start of the execution of the handover procedure is lower than a first preset time period, or twenty pieces of time elapsed since the occurrence of the handover failure are lower than a first preset time period. In some embodiments, whether the first preset time period is reached may be determined by a first timer, wherein the starting time of the first timer may be any one of: when a first handover configuration message is received, when a handover procedure is started, when a handover failure occurs, etc. For example, the number of times a particular event occurs below a number threshold may include any of: the number of times of handover failure is lower than a number threshold, the number of times of fallback success is lower than a number threshold, or the number of times of handover triggering is lower than a number threshold. In some embodiments, it may be determined by a counter whether a number threshold is reached, where the time of initiation (or reset) of the number threshold may be any of: when a handover failure occurs, when a fallback occurs, when the fallback succeeds, or when a handover is triggered, etc.

In other words, if the elapsed time reaches the first preset time period or the number of times a specific event occurs reaches the number threshold, the backoff is not performed any more. The first preset time period and/or the number threshold may be predefined or preconfigured by a protocol, or may be configured by the source network device 232 through higher layer signaling, or may be sent by the source network device 232 to the terminal device 210 through an RRC reconfiguration message, or may be sent by the source network device 232 to the terminal device 210 through other signaling, which is not limited in the embodiment of the present disclosure. In some embodiments, the first preset time period and/or the number threshold may be included in the fallback indication information. In some embodiments, the first preset time period and/or the number threshold may be included in another signaling, independent of the fallback indication information.

At block 522, the terminal device 210 performs a fallback operation. That is, the terminal device 210 reverts to the source cell configuration.

It should be noted that although FIG. 5 shows 520 being performed before 522 being performed after the branch at 520 where "YES" is determined, the disclosure is not so limited. As another example, the process may be performed 522 followed by 520, and the process may be performed 524 after the "YES" branch is determined 520. Are not listed here.

At block 524, the terminal device 210 determines whether the fallback is successful. If so, 526 is performed. If not, 530 is performed.

The successful fallback may mean that the terminal device 210 successfully reverts to the source cell configuration and resumes the connection with the source cell (resume the connection with source cell).

At block 526, the terminal device 210 is maintained at the source cell. That is, the terminal device 210 continues to communicate with the source network device 232.

It is to be appreciated that the terminal device 210 can also re-execute the cell handover procedure after 526. In some embodiments, the terminal device 210 may still perform a cell handover based on the first handover configuration message. For example, 410 through 440 shown in fig. 4 are re-executed. In some embodiments, the terminal device 210 may receive the second handover configuration message from the source network device 232 and perform cell handover based on the second handover configuration message, similar to 410 to 440 as shown in fig. 4. The second handover configuration message may include a new trigger condition and handover configuration information for each of the new candidate cell sets. The new trigger condition in the second handover configuration message may be the same as or different from the trigger condition in the first handover configuration message. The new set of candidate cells indicated in the second handover configuration message may be completely different, partially the same, or all the same as the set of candidate cells indicated in the first handover configuration message. The present disclosure is not limited thereto.

Additionally or alternatively, 528 may also be performed after 522.

At block 528, the terminal device 210 determines whether the first indication information indicates to send a first message to the source network device 232 when a handover failure occurs. If the first indication indicates that the first message was sent to source network device 232 when a handover failure occurred, 529 is performed.

Illustratively, the first indication information may be predefined or preconfigured by a protocol, or may be configured by the source network device 232 through higher layer signaling, or may be sent by the source network device 232 to the terminal device 210 through an RRC reconfiguration message, or may be sent by the source network device 232 to the terminal device 210 through other signaling, which is not limited in the embodiment of the present disclosure.

Alternatively, the fallback indication information and the first indication information may be included in the same signaling. Optionally, the first indication information may further indicate information included in the first message.

At block 529, end device 210 sends a first message to source network device 232.

Alternatively, the first message may be sent upon determining that a link between the terminal device 210 and the source network device 232 is available. Alternatively, the first message may be sent to the source network device 232 directly via a link between the terminal device 210 and the source network device 232.

Alternatively, the first message may be sent indirectly to the source network device 232. For example, the terminal device 210 may send the first message to another network device and forward the first message to the source network device 232 by the other network device. For example, in a case where the link between the terminal device 210 and the source network device 232 has been released, the fallback operation performed by the terminal device 210 to the source cell 222 may result in a fallback failure, at which point the first message may be sent to the source network device 232 via another network device.

The first message may indicate one or more of: a first preset time period or time threshold, a handover type, the number of times of handover failure, the time when handover failure occurs, a first time period from initiation of a handover procedure to occurrence of handover failure, first measurement information for a first target cell when handover failure occurs, second measurement information for a source cell when handover failure occurs, third measurement information for other candidate cells in a candidate cell set when handover failure occurs, whether fallback is performed, the number of times of fallback success, the time when fallback succeeds, fourth measurement information for the first target cell when fallback succeeds, fifth measurement information for the source cell when fallback succeeds, sixth measurement information for other candidate cells when fallback succeeds, a second time period from occurrence of handover failure to fallback success, whether fallback failure occurs, the time when fallback fails, seventh measurement information for the first target cell when fallback fails, eighth measurement information for the source cell when fallback fails, third measurement information for other candidate cells in the candidate cell set when fallback fails, and the like.

Alternatively, the handover type may be DAPS + CHO. The other candidate cells may refer to other candidate cells in the candidate cell set than the first target cell.

It is understood that the terminal device 210 may perform cell handover again after the fallback is successful, and handover failure may also occur again. The number of times the handover failure occurs may refer to the number of times the handover failure occurs since the first handover configuration message was received. The time when the handover failure occurs may include: the time when the handover failure occurs for the first time, the time when the handover failure occurs for the last time (the last time from the current time), or the time when the handover failure occurs each time. The first duration indicated by the first message may include: the length of time between any occurrence of a handover failure and any one (or each or the last) of the handover procedure from the initiation of the handover procedure based on the first handover configuration message. In addition, the first duration from the initiation of the handover procedure to the occurrence of the handover failure may be expressed as: the time length from the initiation of the switching process to the first switching failure, and/or the time length between two adjacent switching failures, etc.

Alternatively, the first measurement information, the second measurement information, and the third measurement information may include a measurement result each time a handover failure occurs, or may include a measurement result when a handover failure occurs last time, respectively.

Alternatively, the number of times of successful backoff indicated by the first message may refer to the number of times of successful backoff within a first preset time period, or may refer to the number of times of successful backoff after receiving the first handover configuration message. The time when the backoff is successful may include: the time when the first backoff was successful, the time when the last backoff was successful (the last backoff from the current time), or the time when each backoff was successful. The fourth, fifth, and sixth measurement information may include a measurement result each time the backoff is successful, or may include a measurement result when the last backoff is successful, respectively.

Optionally, the second duration may include: the time length from the first occurrence of a handover failure to the first success of fallback, the time length from the first occurrence of a handover failure to the last success of fallback, the time length from the last occurrence of a handover failure to the last success of fallback, or the time length from each occurrence of a handover failure to the next most adjacent success of fallback, etc. Optionally, the second duration may further indicate a duration between two consecutive backoff successes, and the like.

Optionally, the third duration may include: the time period from the first occurrence of the handover failure to the fallback failure, or the time period from the last occurrence of the handover failure to the fallback failure, etc.

Additionally or alternatively, the first message may also indicate a number of times the handover is triggered, a time at which the handover is triggered, and/or the like.

Additionally or alternatively, the first message may also indicate measurement information for the at least one neighbor cell of the source cell when the fallback is successful (e.g., last time or every time), and/or measurement information for the at least one neighbor cell of the source cell when the fallback fails.

Additionally or alternatively, the first message may also indicate measurement information for the indicated cell of the source cell when the fallback is successful (e.g., last time or every time) and/or measurement information for the indicated cell of the source cell when the fallback fails. For example, the source network device 232 may notify the terminal device 210 of the indicated cell identifier in advance through signaling, where the signaling may be an RRC reconfiguration message or may be another message, which is not limited by the present disclosure. Then, the terminal device 210 may measure the indicated cell based on the identity of the indicated cell to obtain measurement information, and indicate the measurement information of the indicated cell through the first message.

The measurement information in the embodiments of the present disclosure may be a measurement result obtained by performing measurement on a measurement object, where the measurement object may be a synchronization signal, a reference signal, or the like, and for example, one or more of the following may be included: channel State Information Reference Signal (CSI-RS), synchronization Signal and Physical Broadcast Channel Block (SSB), and the like. The measurement may be a beam level or cell level measurement, for example including one or more of: reference Signal Received Power (RSRP), reference Signal Received Quality (RSRQ), signal to Noise Ratio (SINR), received Signal Strength Indication (RSSI), and the like.

Optionally, the first message may be carried in a handover failure (HO failure) report, or the first message may be another message independent of the handover failure report, which is not limited by the present disclosure.

At block 530, the terminal device 210 performs cell selection. In particular, this process may also be referred to as cell reselection, and the terminal device 210 may determine whether there is a cell that satisfies the trigger condition.

In block 540, the terminal device 210 determines whether a suitable cell cannot be found within a second preset time period.

In some embodiments, the second preset time period may be received from the source network device 232. For example, the second preset time period may be included in the first handover configuration message to indicate an occasion to perform cell selection. As another example, the second preset time period may be included in other signaling or messages. In some embodiments, the second preset time period may be predefined by a protocol or may be preconfigured, which is not limited by this disclosure.

In some embodiments, the terminal device 210 may use a second timer to determine whether a second preset time period has been reached, wherein the starting time of the second timer may be any of the following: when a first handover configuration message is received, when a handover procedure is started, when a handover failure occurs, or when a fallback failure occurs, etc.

Specifically, it may be determined whether a cell satisfying the trigger condition can be found within a second preset time period. If a suitable cell cannot be found within a second preset time period, 532 is performed. If a suitable cell is found within the second preset time period, proceed to 533.

At block 532, the terminal device 210 enters an idle state. Specifically, if the terminal device 210 cannot find a suitable cell within the second preset time period, the terminal device enters an idle state, and cell selection is avoided for a long time, so that energy consumption of the terminal device 210 can be saved.

At block 533, the terminal device 210 determines whether the selected cell is a candidate cell.

In particular, it may be determined whether the new cell determined at 530 to perform cell selection belongs to the candidate set of cells. As previously described, the source network device 232 has sent the handover configuration information for each candidate cell in the candidate cell set to the terminal device 210.

As an example, assuming the new cell is the second target cell 226, which belongs to the candidate set of cells, 535 is performed. Conversely, assuming the new cell is a third target cell, which does not belong to the candidate set of cells, 534 is performed.

At block 534, the terminal device 210 performs RRC reestablishment. And 535 may then be performed.

Alternatively, as another implementation, the "no" branch at 531 may be followed by execution 534 and then execution 535. That is, 533 may not be performed.

At block 535, the terminal device 210 performs a cell handover. Specifically, the terminal device 210 is handed over from the source cell to a new cell, such as the second target cell 226 or the third target cell.

At block 536, the terminal device 210 determines whether the handover failed. If it is determined that the handover failed, execution 510 may be returned. If the switch is determined to be successful 537.

At block 537, the terminal device 210 camps on a new cell. In particular, referring to fig. 3, after the handover is successful, an RRC reconfiguration complete message may be sent to the network device of the new cell (e.g., the second target network device 236 or the network device of the third target cell). Optionally, a detach from the source cell may also be performed.

Additionally or alternatively, 538 may also be performed if the handover is determined to be successful at 536.

At block 538, the terminal device 210 sends a second message.

In some embodiments, the terminal device 210 may send a second message to the source network device 232. For example, the terminal device 210 may send a second message to the source network device 232 prior to separation from the source cell. Alternatively, terminal device 210 may send the second message to another network device and forward the second message to source network device 232 by the other network device.

In some examples, the other network device may be a network device of the new cell, that is, terminal device 210 may send the second message directly or indirectly to the network device of the new cell, so that the network device of the new cell may forward the second message directly or indirectly to source network device 232. For example, assuming that the network device of the new cell is the second target network device 236, the terminal device 210 may send a second message to the second target network device 236. Optionally, the second message may be included in an RRC reconfiguration complete message sent by the terminal device 210 to the network device of the new cell. After which the second target network device 236 may forward the second message to the source network device 232. Alternatively, the second target network device 236 may combine the second message with the handover complete message into one message to send to the source network device 232.

In some examples, the other network device may be indicated by the first handover configuration message sent by the source network device 232. For example, the first handover configuration message may include the identities of the other cells. The terminal device 210 may thus determine the network device of the other cell based on the identity of the other cell, and the terminal device 210 may send the second message directly or indirectly to the network device of the other cell indicated by the identity, so that the network device of the other cell may forward the second message directly or indirectly to the source network device 232.

The second message may indicate one or more of: a first preset time period or time threshold, a handover type, the number of times of handover failure, the time when handover failure occurs, a first time period from initiation of a handover procedure to occurrence of handover failure, first measurement information for a first target cell when handover failure occurs, second measurement information for a source cell when handover failure occurs, third measurement information for other candidate cells when handover failure occurs, whether or not to perform fallback, the number of times of success of fallback, the time when fallback succeeds, fourth measurement information for the first target cell when fallback succeeds, fifth measurement information for the source cell when fallback succeeds, sixth measurement information for other candidate cells in a candidate cell set when fallback succeeds, a second time period from occurrence of handover failure to success, whether or not to fallback fails, the time when fallback fails, seventh measurement information for the first target cell when fallback fails, eighth measurement information for the source cell when fallback fails, third measurement information for other candidate cells in the candidate cell set when fallback fails, and fourth measurement information from occurrence of handover failure to ninth target cell when fallback fails; or a fifth time period from the occurrence of the handover failure to the successful selection of the second target cell, etc.

It is understood that the terminal device 210 may perform cell handover again after the fallback is successful, and handover failure may also occur again. The number of times of occurrence of the handover failure may refer to the number of times of occurrence of the handover failure since the reception of the first handover configuration message. The time when the handover failure occurs may include: the time when the handover failure occurs for the first time, the time when the handover failure occurs for the last time (the last time from the current time), or the time each time the handover failure occurs. The first time period may include: the length of time between any occurrence of a handover failure from the initiation of a handover procedure based on the first handover configuration message to any one (or each or last) occurrence. In addition, the first duration from the initiation of the handover procedure to the occurrence of the handover failure may be expressed as: the time length from the initiation of the switching process to the first switching failure, and/or the time length between two adjacent switching failures, etc.

Alternatively, the number of times of successful backoff may refer to the number of times of successful backoff within a first preset time period, or may refer to the number of times of successful backoff after receiving the first handover configuration message. The time when the backoff is successful may include: the time when the first backoff was successful, the time when the last backoff was successful (the last backoff from the current time), or the time when each backoff was successful. The fourth, fifth, and sixth measurement information may include a measurement result every time the backoff is successful, or may include a measurement result of the last successful backoff, respectively.

Optionally, the third duration may include: the time period from the first occurrence of the handover failure to the fallback failure, the time period from the last occurrence of the handover failure to the fallback failure, and the like.

Optionally, the fifth duration may include: the duration from the first occurrence of the handover failure to the successful selection of the second target cell, the duration from the last occurrence of the handover failure to the successful selection of the second target cell, the duration from each occurrence of the handover failure to the successful selection of the second target cell, and the like. In addition, the fifth time period may also be expressed as a time period from the occurrence of the handover failure to the selection of the suitable cell, for example. Further, for example, the fifth time period may be indicated indirectly, for example, the fifth time period may be indicated by a sum of the third time period and the fourth time period.

Additionally or alternatively, the second message may also indicate a number of times the handover is triggered, a time at which the handover is triggered, and/or the like.

Additionally or alternatively, the second message may also indicate measurement information for the at least one neighbor cell of the source cell when the fallback is successful (e.g., last time or every time), and/or measurement information for the at least one neighbor cell of the source cell when the fallback fails.

Additionally or alternatively, the second message may also indicate measurement information for the cell indicated by the source cell when the fallback is successful (e.g., last time or every time) and/or measurement information for the cell indicated by the source cell when the fallback fails. For example, the source network device 232 may notify the terminal device 210 of the indicated cell identifier in advance through signaling, where the signaling may be an RRC reconfiguration message or may be another message, which is not limited by the present disclosure. Then, the terminal device 210 may measure the indicated cell based on the identity of the indicated cell to obtain measurement information, and indicate the measurement information of the indicated cell through the second message.

The measurement information may be a measurement result obtained by performing measurement on a measurement object, where the measurement object may be a synchronization signal, a reference signal, or the like, and for example, one or more of the following items are included: CSI-RS, SSB, etc. The measurement may be a beam level or cell level measurement, for example including one or more of: RSRP, RSRQ, SINR, RSSI, etc.

In addition, the handover type indicated by the first message or the second message may be a hybrid handover type, or may also be referred to as DAPS + CHO. Alternatively, the handover type may be a handover based on the fallback indication information. It should be noted, however, that the present disclosure is not so limited, e.g., the handover type may be a DAPS handover, or the handover type may be a CHO, or the handover type may be another type, which is not listed here.

Thus, when the terminal device fails to perform handover, it may determine whether to fallback to the source cell or re-execute cell selection based on the fallback indication information, so that the processing flow of the terminal device may be determined, and the handover efficiency is ensured.

Fig. 6 shows a schematic flow diagram of a process 600 for cell handover in accordance with some embodiments of the present disclosure. Process 600 may be performed by a network device, such as network device 232 shown in FIG. 2, and the like.

In block 610, the network device 232 sends fallback indication information to the terminal device 210, where the fallback indication information indicates at least whether to fallback to the source cell 222 when the handover fails, and the network device 232 is a network device of the source cell when the terminal device 210 performs a handover procedure.

Alternatively, the fallback indication information may be included in the RRC reconfiguration message, or the fallback indication information may be included in other messages. The transmission timing of the fallback indication information is not limited in the embodiments of the present disclosure, and may be indicated in system information, may be indicated in RRC signaling, may be indicated in a random access response, or may be indicated in a handover configuration message, for example.

Additionally or alternatively, the network device 232 may further send a first handover configuration message to the terminal device 210, where the first handover configuration message may include a trigger condition and handover configuration information of each candidate cell in the candidate cell set, where the trigger condition is at least used for the terminal device to determine the first target cell. In some embodiments, the first handover configuration message may be implemented as an RRC reconfiguration message.

In block 620, when the terminal device 210 has failed handover during handover and the fallback indication information indicates fallback to the source cell when the handover fails, the network device 232 performs an operation of connecting with the terminal device 210 based on the fallback operation of the terminal device 210.

When the fallback indication information indicates to fallback to the source cell upon handover failure, in conjunction with fig. 2, if the terminal device 210 performs a fallback operation to the cell 222 in case that the handover failure occurs in the handover procedure of the terminal device 210 from the cell 222 to the cell 224, the network device 232 may recover the connection with the terminal device 210.

Additionally or alternatively, at block 630, the network device 232 receives a handover report message from the terminal device 210. The handover report message may indicate at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell to which a handover procedure is handed over when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful backspacing; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells when the backoff is successful; a second duration between occurrence of a handover failure and success of fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of fallback failure; a third duration between occurrence of a handover failure and a fallback failure; a fourth duration from the failure of fallback to the successful selection of the new camped cell; or a fifth time period from the occurrence of the handover failure to the successful selection of the new camping cell, etc.

The handover report message may be the first message or the second message in the above embodiments, and the handover report message may be implemented as a handover failure report or a handover success report, which is not limited in this disclosure.

In an embodiment of the present disclosure, the network device 232 may further adjust or update the handover configuration based on the first message, for example, may determine the second handover configuration message. For example, if the terminal device 210 successfully backs up, the network device 232 may further send a second handover configuration message to the terminal device 210 that successfully backs up, so that the terminal device 210 may re-execute the handover procedure based on the second handover configuration message, which can improve the success rate of handover. For example, if the terminal device 210 fails to fallback, the network device 232 may send a second handover configuration message to other terminal devices to be handed over, so as to reduce the probability of handover failure of the other terminal devices to be handed over in the cell handover process.

Embodiments of the present disclosure do not limit the specific manner in which the network device 232 adjusts or updates the handover configuration. For example, if the third duration indicated in the message is short (below a preset first duration threshold, such as 2 seconds or other value), then the network device 232 may determine that the link quality of the terminal device 210 and the source cell at the time of handover is too poor, or may determine that the link quality of the terminal device 210 and the target cell at the time of handover is better. Alternatively, the network device 232 may determine that the terminal device 210 is not suitable to fallback to the source cell, or the network device 232 may determine that the terminal device 210 last selected the wrong target cell. Alternatively, the network device 232 may send new fallback indication information to the terminal device 210, indicating that the terminal device 210 does not fallback when the handover fails. Optionally, the network device 232 may send second handover configuration information to the terminal device 210, which indicates the other candidate cell sets. For example, if the third duration indicated by the message is long (exceeds a preset second duration threshold, such as 5 seconds or other value), then network device 232 may determine that the last handover failure may be a premature handover due to unreasonable handover configuration.

It is to be understood that reference may be made to the above embodiments in connection with fig. 3 to 5 regarding the fallback indication information, the first message, the second message, etc., which are not repeated here for brevity.

Therefore, in the embodiment of the disclosure, the network device may adjust the mobility parameter based on the indication about the various information in the handover process reported by the terminal device, so that the success rate of the handover performed by the terminal device can be improved, and the occurrence of handover failure is reduced.

It should be understood that in the embodiments of the present disclosure, "first", "second", "third", etc. are only intended to indicate that a plurality of objects may be different, but at the same time do not exclude the same between two objects. The terms "first," "second," "third," and the like, should not be construed as limiting any of the embodiments of the disclosure.

It should also be understood that the manner, the case, the category, and the division of the embodiments of the present disclosure are for convenience of description only and should not be construed as a particular limitation, and features of various manners, categories, cases, and embodiments may be combined with each other in a case where they are logically consistent.

It should also be understood that the above-described contents are only for helping those skilled in the art to better understand the embodiments of the present disclosure, and are not intended to limit the scope of the embodiments of the present disclosure. Various modifications or changes or combinations thereof will occur to those skilled in the art in light of the foregoing description. Such modifications, variations, or combinations are also within the scope of the embodiments of the present disclosure.

It should also be understood that the above description focuses on emphasizing different points before the embodiments, and that the same or similar points may be referred to or referred to each other, and for brevity, are not described again.

Fig. 7 illustrates a schematic block diagram of a communication apparatus 700 for cell handover in accordance with some embodiments of the present disclosure. The apparatus 700 may be implemented as the terminal device 210 or as a part (e.g., a chip) of the terminal device 210, etc., and the disclosure is not limited thereto.

As shown in fig. 7, the apparatus 700 may include a switching module 710, a first determining module 720, a second determining module 730, and a fallback module 740. Additionally optionally, the apparatus 700 may further include a cell selection module 750, a reconstruction module 760, a conversion module 770, and a transmission module 780.

The handover module 710 is configured to perform a handover procedure from a source cell to a first target cell, the first target cell belonging to a set of candidate cells. The first determination module 720 is configured to determine that a handover failure occurs in a handover procedure. The second determining module 730 is configured to determine fallback indication information indicating at least whether to fallback to the source cell upon handover failure. The fallback module 740 is configured to perform a fallback operation to the source cell when the fallback indication information indicates fallback to the source cell upon handover failure.

Illustratively, the cell selection module 750 may be configured to perform the cell selection procedure when an elapsed time from initiation of the handover procedure reaches a first preset time period or when a number of times of occurrence of handover failures reaches a number threshold. Illustratively, the cell selection module 750 may be configured to perform the cell selection procedure by the terminal device when the elapsed time reaches a first preset time period or the number of times of occurrence of a specific event reaches a threshold number, wherein a starting time of the first preset time period may be when the first handover configuration message is received, when the handover procedure is started, or when a handover failure occurs; wherein the specific event may be when a handover failure occurs, when a fallback occurs, when the fallback succeeds, or when a handover is triggered.

Alternatively, the cell selection module 750 may be configured to perform a cell selection procedure when it is determined that the fallback operation fails. Alternatively, the cell selection module 750 may be configured to perform the cell selection procedure when the fallback indication information indicates not to fallback to the source cell upon handover failure.

In some embodiments, the transmitting module 780 may be configured to transmit a first message to the network device of the source cell, the first message indicating at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful backspacing; time when rollback is successful; fourth measurement information for the first target cell each time the fallback succeeds; fifth measurement information for the source cell each time the fallback is successful; sixth measurement information for other candidate cells at each successful backoff; a second duration between the occurrence of the handover failure and the success of the fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of failure of the fallback; or a third time period from the occurrence of the handover failure to the fallback failure.

Optionally, the handover module 710 may be further configured to perform a handover procedure to a second target cell in the candidate set of cells when the cell selection procedure selects the second target cell. The re-establishment module 760 may be configured to perform an RRC re-establishment procedure with a second target cell that does not belong to the candidate cell set when the cell selection procedure selects the second target cell. Or alternatively, the re-establishment module 760 may be configured to perform an RRC re-establishment procedure with the second target cell when the second target cell is selected by the cell selection procedure.

The transition module 770 may be configured to transition to the idle state when a suitable cell cannot be found within a second preset time period.

In some embodiments, the transmitting module 780 may be configured to transmit the second message when the cell selection procedure selects the second target cell and successfully hands over to the second target cell. The second message indicates at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells in the candidate cell set when the fallback is successful; a second duration between occurrence of a handover failure and success of fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of fallback failure; a third duration between occurrence of a handover failure and a fallback failure; a fourth time period from the fallback failure to the successful selection of the second target cell; or a fifth time period from the occurrence of the handover failure to the successful selection of the second target cell.

It is understood that the division of the modules or units in the embodiments of the present disclosure is schematic, and is only a logical division, and in actual implementation, there may be another division manner, and in addition, each functional unit in the embodiments of the present disclosure may be integrated into one unit, or may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The apparatus 700 in fig. 7 can be used to implement the processes described by the terminal device 210 in the foregoing embodiments, and for brevity, details are not described here again.

Fig. 8 illustrates one schematic block diagram of a communication apparatus 800 for cell handover in accordance with some embodiments of the present disclosure. Apparatus 800 may be implemented as network device 232 or as a portion (e.g., a chip) of network device 232, etc., to which the present disclosure is not limited.

As shown in fig. 8, the apparatus 800 includes a transmitting module 810, a connecting module 820, and a receiving module 830. The sending module 810 is configured to send fallback indication information to the terminal device, where the fallback indication information indicates at least whether to fallback to a source cell when handover fails, and the communication apparatus 800 is a network device of the source cell when the terminal device performs a handover procedure. The connection module 820 is configured to perform an operation of connecting with the terminal device based on a fallback operation of the terminal device when the terminal device has a handover failure during a handover procedure and the fallback indication information indicates to fallback to a source cell at the time of the handover failure.

Optionally, the sending module 810 may be further configured to send a handover configuration message to the terminal device, where the handover configuration message may include a trigger condition and handover configuration information of each candidate cell in the candidate cell set, where the trigger condition is at least used for the terminal device to determine the first target cell.

In some embodiments, the receiving module 830 may be configured to receive a handover report message from the terminal device, the handover report message indicating at least one of: a first preset time period or time threshold; a handover type of the handover procedure; the number of times of handover failures; time when handover failure occurs; a first duration from initiation of a handover procedure to occurrence of a handover failure; first measurement information for a first target cell to which a handover procedure is handed over when a handover failure occurs; second measurement information for the source cell when a handover failure occurs; third measurement information for other candidate cells in the candidate cell set when a handover failure occurs; whether to perform rollback; the number of successful rollback; time when rollback is successful; fourth measurement information for the first target cell when the fallback is successful; fifth measurement information for the source cell when the fallback is successful; sixth measurement information for other candidate cells when the backoff is successful; a second duration between the occurrence of the handover failure and the success of the fallback; whether rollback has failed; time when rollback failed; seventh measurement information for the first target cell when fallback fails; eighth measurement information for the source cell when fallback fails; ninth measurement information for other candidate cells in the candidate cell set at the time of failure of the fallback; a third duration between occurrence of a handover failure and a fallback failure; a fourth duration from the failure of fallback to the successful selection of the camped cell; or a fifth time period from the occurrence of a handover failure to the successful selection of the camped cell.

It is understood that the division of the modules or units in the embodiments of the present disclosure is schematic, and is only a logical division, and in actual implementation, there may be another division manner, and in addition, each functional unit in the embodiments of the present disclosure may be integrated into one unit, or may exist alone physically, or two or more units are integrated into one unit. The integrated unit may be implemented in the form of hardware, or may also be implemented in the form of a software functional unit.

The apparatus 800 in fig. 8 can be used to implement the various processes described by the network device 232 in the foregoing embodiments, and for brevity, details are not described here again.

Fig. 9 illustrates a schematic block diagram of an example device 900 that may be used to implement embodiments of the present disclosure. Device 900 may be implemented as or included in terminal device 210 of fig. 2, or device 900 may be implemented as or included in network device 232 of fig. 2. As shown, the device 900 includes one or more processors 910, one or more memories 920 coupled to the processors 910, and a communication module 940 coupled to the processors 910.

The communication module 940 may be used for bidirectional communication. The communication module 940 may have at least one communication interface for communication. The communication interface may include any interface necessary to communicate with other devices.

The processor 910 may be of any type suitable for a local technology network, and may include, but is not limited to, at least one of: one or more of a general purpose computer, a special purpose computer, a microcontroller, a Digital Signal Processor (DSP), or a controller-based multi-core controller architecture. Device 900 may have multiple processors, such as application specific integrated circuit chips, that are time dependent from a clock synchronized to the main processor.

The memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, at least one of: read-Only Memory (ROM) 924, erasable Programmable Read Only Memory (EPROM), flash Memory, a hard disk, an optical disk (CD), a Digital Video Disk (DVD), or other magnetic and/or optical storage. Examples of volatile memory include, but are not limited to, at least one of: random Access Memory (RAM) 922, or other volatile Memory that does not last for the duration of the power down.

Computer programs 930 include computer-executable instructions that are executed by associated processor 910. The program 930 may be stored in the ROM 924. Processor 910 can perform any suitable actions and processes by loading program 930 into RAM 922.

Embodiments of the present disclosure may be implemented by way of the program 930 such that the device 900 may perform any of the processes as discussed with reference to fig. 4-6. Embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

Program 930 can be tangibly embodied in a computer-readable medium, which can be included in device 900 (such as in memory 920) or other storage device accessible by device 900. The program 930 may be loaded from the computer-readable medium into the RAM 922 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, a hard disk, a CD, a DVD, etc.

In some embodiments, the communication module 940 in the device 900 may be implemented as a transmitter and a receiver (or transceiver) which may be configured to transmit/receive information such as a handover configuration message, fallback indication information, a first message, a second message, and the like. Additionally, the device 900 may further include one or more of a scheduler, a controller, and a radio frequency/antenna, which are not elaborated in this disclosure.

Illustratively, the apparatus 900 in fig. 9 may be implemented as a communication device, or may be implemented as a chip or a chip system in a communication device, to which the embodiments of the disclosure are not limited.

Embodiments of the present disclosure also provide a chip that may include an input interface, an output interface, and a processing circuit. In the embodiment of the present disclosure, the interaction of signaling or data can be completed by the input interface and the output interface, and the generation and processing of signaling or data information can be completed by the processing circuit.

Embodiments of the present disclosure also provide a chip system, including a processor, configured to support a device to implement the functions recited in any of the above embodiments. In one possible design, the system-on-chip may further include a memory for storing necessary program instructions and data, which when executed by the processor, cause the device on which the system-on-chip is installed to implement the method according to any of the above embodiments. Illustratively, the chip system may be composed of one or more chips, and may also include chips and other discrete devices.

Embodiments of the present disclosure also provide a processor coupled with a memory, the memory storing instructions that, when executed by the processor, cause the processor to perform the methods and functions recited in any of the above embodiments.

Embodiments of the present disclosure also provide a computer program product containing instructions which, when run on a computer, cause the computer to perform the methods and functions referred to in any of the embodiments described above.

Embodiments of the present disclosure also provide a computer-readable storage medium having stored thereon computer instructions, which, when executed by a processor, cause the processor to perform the methods and functions recited in any of the above embodiments.

In general, the various embodiments of the disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor or other device. While various aspects of the embodiments of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer executable instructions, such as instructions included in program modules, which are executed in a device on a real or virtual processor of the target to perform the processes/methods as described above with reference to the figures. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed facility, program modules may be located in both local and remote memory storage media.

Computer program code for implementing the methods of the present disclosure may be written in one or more programming languages. These computer program code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the computer or other programmable data processing apparatus, causes the functions/acts specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the computer, partly on the computer, as a stand-alone software package, partly on the computer and partly on a remote computer or entirely on the remote computer or server.

In the context of the present disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations described above. Examples of a carrier include a signal, computer readable medium, and the like. Examples of signals may include electrical, optical, radio, acoustic, or other forms of propagated signals, such as carrier waves, infrared signals, and the like.

The computer readable medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More detailed examples of a computer-readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical storage device, a magnetic storage device, or any suitable combination thereof.

Further, while the operations of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions. It should also be noted that the features and functions of two or more devices according to the present disclosure may be embodied in one device. Conversely, the features and functions of one apparatus described above may be further divided into embodiments by a plurality of apparatuses.

The foregoing has described implementations of the present disclosure, and the above description is illustrative, not exhaustive, and not limited to the implementations disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described implementations. The choice of terms used herein is intended to best explain the principles of the implementations, practical applications, or improvements to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the various implementations disclosed herein.

Claims

1. A cell handover method, comprising:

the terminal equipment executes a switching process from a source cell to a first target cell, wherein the first target cell belongs to a candidate cell set;

the terminal equipment determines that a switching failure occurs in the switching process;

the terminal equipment determines backspacing indication information, wherein the backspacing indication information at least indicates whether to backspace to a source cell when the switching fails; and

when the fallback indication information indicates to fallback to a source cell when handover fails, the terminal device executes a fallback operation to the source cell.

2. The method of claim 1, further comprising:

and when the time elapsed from the initiation of the switching process reaches a first preset time period or the number of times of switching failure reaches a threshold value, the terminal equipment executes a cell selection process.

3. The method of claim 1, further comprising:

and when the rollback operation is determined to fail, the terminal equipment executes a cell selection process.

4. The method of claim 1, further comprising:

and when the fallback indication information indicates not to fallback to the source cell when the handover fails, the terminal equipment executes a cell selection process.

5. The method of claim 2, wherein the fallback indication information further indicates at least one of: the first preset time period or the number threshold.

6. The method of any of claims 1 to 3, further comprising:

the terminal equipment sends a first message to the network equipment of the source cell, wherein the first message indicates at least one of the following:

a first preset time period or time threshold;

a handover type of the handover procedure;

the number of times of handover failures;

time when the handover failure occurs;

a first duration from initiation of the handover procedure to occurrence of the handover failure;

first measurement information for the first target cell when the handover failure occurs;

second measurement information for the source cell when the handover failure occurs;

third measurement information for other candidate cells in the set of candidate cells when the handover failure occurs;

whether to perform rollback;

the number of successful rollback;

time when rollback is successful;

fourth measurement information for the first target cell when fallback is successful;

fifth measurement information for the source cell when the fallback is successful;

sixth measurement information for the other candidate cells when the fallback is successful;

a second duration between the occurrence of the handover failure and the success of the fallback;

whether rollback has failed;

time when rollback failed;

seventh measurement information for the first target cell when fallback fails;

eighth measurement information for the source cell when fallback fails;

ninth measurement information for other candidate cells in the set of candidate cells at the time of fallback failure; or

A third duration from the occurrence of the handover failure to the fallback failure.

7. The method of any of claims 2 to 4, further comprising:

when the cell selection procedure selects a second target cell in the candidate cell set, the terminal device performs a handover procedure to the second target cell;

when the cell selection process selects a second target cell not belonging to the candidate cell set, the terminal device performs a radio resource control, RRC, reestablishment process with the second target cell; or

And when the suitable cell cannot be found within a second preset time period, the terminal equipment is converted into an idle state.

8. The method of any of claims 2 to 4, further comprising:

when the cell selection process selects a second target cell, the terminal device executes an RRC reestablishment process with the second target cell; or

9. The method of claim 7 or 8, further comprising:

when the cell selection procedure selects the second target cell and successfully switches to the second target cell, the terminal device sends a second message indicating at least one of:

a first preset time period or time threshold;

a handover type of the handover procedure;

the number of times of handover failures;

time when the handover failure occurs;

third measurement information for other candidate cells in the set of candidate cells upon occurrence of the handover failure;

whether to perform rollback;

the number of successful rollback;

time when rollback is successful;

sixth measurement information for other candidate cells in the candidate cell set when fallback is successful;

a second duration between occurrence of a handover failure and success of fallback;

whether rollback has failed;

time when rollback failed;

seventh measurement information for the first target cell upon a fallback failure;

eighth measurement information for the source cell when fallback fails;

ninth measurement information for other candidate cells in the set of candidate cells at the time of fallback failure;

a third duration between occurrence of a handover failure and a fallback failure;

a fourth duration between a fallback failure and a successful selection of the second target cell; or

A fifth duration from the occurrence of the handover failure to the successful selection of the second target cell.

10. The method according to any of claims 1 to 9, wherein the fallback indication information is received from a network device of the source cell, or wherein the fallback indication information is preconfigured in the terminal device.

11. A method of cell handover, comprising:

the network equipment sends back indication information to the terminal equipment, wherein the back indication information at least indicates whether the terminal equipment backs to a source cell when the switching fails, and the network equipment is the network equipment of the source cell when the terminal equipment executes the switching process; and

when the terminal equipment fails to switch in the switching process and the fallback indication information indicates to fallback to a source cell when the terminal equipment fails to switch, the network equipment executes the operation of connecting with the terminal equipment based on the fallback operation of the terminal equipment.

12. The method of claim 11, further comprising:

the network device receives a handover report message from the terminal device, the handover report message indicating at least one of:

a first preset time period or time threshold;

a handover type of the handover procedure;

the number of times of handover failures;

time when the handover failure occurs;

first measurement information for a first target cell to which the handover procedure is handed over when the handover failure occurs;

third measurement information for other candidate cells in the set of candidate cells at the occurrence of the handover failure;

whether to perform rollback;

the number of successful rollback;

time when rollback is successful;

whether rollback has failed;

time when rollback failed;

seventh measurement information for the first target cell when fallback fails;

eighth measurement information for the source cell when fallback fails;

a fourth time period from the fallback failure to the successful selection of the camped cell; or

A fifth time period from the occurrence of the handover failure to the successful selection of the camped cell.

13. A communication device, comprising:

a handover module configured to perform a handover procedure from a source cell to a first target cell, the first target cell belonging to a set of candidate cells;

a first determining module configured to determine that a handover failure occurs in the handover procedure;

a second determining module configured to determine fallback indication information indicating at least whether to fallback to a source cell upon handover failure; and

a fallback module configured to perform a fallback operation to a source cell when the fallback indication information indicates fallback to the source cell upon handover failure.

14. The apparatus of claim 13, further comprising a cell selection module configured to:

performing a cell selection procedure when an elapsed time from initiation of the handover procedure reaches a first preset time period or when a number of times of occurrence of handover failure reaches a number threshold.

15. The apparatus of claim 13, further comprising a cell selection module configured to:

and when the rollback operation is determined to fail, executing a cell selection process.

16. The apparatus of claim 13, further comprising a cell selection module configured to:

and when the fallback indication information indicates not to fallback to the source cell when the handover fails, performing a cell selection procedure.

17. The apparatus of claim 14, wherein the fallback indication information further indicates at least one of: the first preset time period or the number threshold.

18. The apparatus of any of claims 13 to 15, further comprising a transmitting module configured to:

sending a first message to a network device of the source cell, the first message indicating at least one of:

a first preset time period or time threshold;

a handover type of the handover procedure;

the number of times of handover failures;

time when the handover failure occurs;

whether to perform rollback;

the number of successful rollback;

time of success of rollback;

whether rollback has failed;

time when rollback failed;

seventh measurement information for the first target cell when fallback fails;

eighth measurement information for the source cell at the time of the fallback failure;

19. The apparatus according to any of claims 14 to 16, wherein the handover module is further configured to perform a handover procedure to a second target cell of the candidate set of cells when the cell selection procedure selects the second target cell;

further comprising a re-establishment module configured to perform a radio resource control, RRC, re-establishment procedure with a second target cell not belonging to the set of candidate cells when the cell selection procedure selects the second target cell; or

The method further comprises a switching module configured to switch to an idle state when a suitable cell cannot be found within a second preset time period.

20. The apparatus of any of claims 14 to 16, further comprising:

a reestablishment module configured to perform an RRC reestablishment procedure with a second target cell when the cell selection procedure selects the second target cell; or

And the switching module is configured to switch to an idle state when a suitable cell cannot be found within a second preset time period.

21. The apparatus of claim 19 or 20, further comprising a transmitting module configured to:

sending a second message when the cell selection procedure selects the second target cell and successfully hands over to the second target cell, the second message indicating at least one of:

a first preset time period or time threshold;

a handover type of the handover procedure;

the number of times of handover failures;

time when the handover failure occurs;

whether to perform rollback;

the number of successful rollback;

time when rollback is successful;

sixth measurement information for other candidate cells in the set of candidate cells when fallback is successful;

whether rollback has failed;

time when rollback failed;

seventh measurement information for the first target cell when fallback fails;

A fifth time period from the occurrence of the handover failure to the successful selection of the second target cell.

22. The apparatus according to any of claims 13 to 21, wherein the fallback indication information is received from a network device of the source cell, or wherein the fallback indication information is preconfigured in the communication apparatus.

23. A communication device, comprising:

a sending module, configured to send fallback indication information to a terminal device, where the fallback indication information at least indicates whether to fallback to a source cell when handover fails, and the communication apparatus is a network device of the source cell when the terminal device executes a handover procedure; and

a connection module configured to execute an operation of connecting with the terminal device based on a fallback operation of the terminal device when the terminal device has a handover failure in a handover process and the fallback indication information indicates to fallback to a source cell when the terminal device fails in handover.

24. The apparatus of claim 23, further comprising a receiving module configured to:

receiving a handover report message from the terminal device, the handover report message indicating at least one of:

a first preset time period or time threshold;

a handover type of the handover procedure;

the number of times of handover failures;

time when the handover failure occurs;

whether to perform rollback;

the number of successful rollback;

time of success of rollback;

whether rollback has failed;

time when rollback failed;

seventh measurement information for the first target cell when fallback fails;

eighth measurement information for the source cell when fallback fails;

a fourth duration from the failure of fallback to the successful selection of the camped cell; or

25. A computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the method of any one of claims 1 to 12.

26. A computer program product having computer-executable instructions embodied thereon that, when executed, implement the method of any one of claims 1 to 12.

27. A chip comprising processing circuitry configured to perform the method of any of claims 1 to 12.