WO2020061899A1 - Procédé et dispositif de commutation de cellule - Google Patents

Procédé et dispositif de commutation de cellule Download PDF

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Publication number
WO2020061899A1
WO2020061899A1 PCT/CN2018/107939 CN2018107939W WO2020061899A1 WO 2020061899 A1 WO2020061899 A1 WO 2020061899A1 CN 2018107939 W CN2018107939 W CN 2018107939W WO 2020061899 A1 WO2020061899 A1 WO 2020061899A1
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WO
WIPO (PCT)
Prior art keywords
cell
terminal device
candidate
handover
candidate cell
Prior art date
Application number
PCT/CN2018/107939
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English (en)
Chinese (zh)
Inventor
唐珣
王宏
张戬
Original Assignee
华为技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to PCT/CN2018/107939 priority Critical patent/WO2020061899A1/fr
Publication of WO2020061899A1 publication Critical patent/WO2020061899A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports

Definitions

  • This application relates to the field of communications, and more specifically, to a method and device for cell handover.
  • the handover of the serving cell can occur according to the change in signal strength.
  • the serving cell handover occurs at the cell edge, the inter-frequency interference problem between cells is serious, and the cell signal strength changes faster.
  • the terminal equipment can only start a radio resource control (radio resource control (RRC) connection re-establishment process). If the terminal equipment's signal strength drops suddenly after receiving the handover command, the terminal equipment will not be able to complete the handover process, and the RRC connection re-establishment will also begin at this time.
  • RRC radio resource control
  • the terminal device switches back to the source base station. This type of handover is called ping pong handover.
  • the handover command When the handover command is sent too early, it may cause a ping-pong handover; if the handover command is sent too late, it may cause a handover failure. Both the RRC connection re-establishment and the ping-pong handover after the handover failure will generate additional signaling overhead, resulting in a waste of system resources.
  • conditional handover technology is introduced.
  • the time point of the switching is determined by the terminal device according to the configured switching conditions, but there is no perfect conditional switching technology for handling abnormal scenarios.
  • the present application provides a method and device for cell switching to ensure that a terminal device can select a target cell with better communication quality, thereby ensuring the communication quality between the terminal device and the base station.
  • a cell switching method including: a terminal device starts a timer; in a case where the timer expires and the terminal device does not determine a target cell to be switched from the first candidate cell set, the The terminal device sends a measurement report to the network device, and the measurement report is used to determine the second candidate cell set; the terminal device receives information of the second candidate cell set from the network device, and determines a target cell to be switched from the second candidate cell set.
  • a timer can be set to prevent the terminal device from reporting the measurement of a cell with poor communication quality. Report; In addition, through the newly defined P1 event, a new candidate cell is reported within the operating time after the timer is started to ensure that the terminal device can select a cell with better communication quality for handover.
  • the candidate cell list of the terminal device for example, performing addition or deletion of cells in the candidate cell list, or adjusting the validity period of the pre-allocated random access resources of the candidate cell, thereby ensuring that the terminal device can select a more suitable target cell To ensure the communication quality between the terminal device and the base station.
  • the timer may be an expiration timer configured for the terminal device.
  • the source base station may configure a measurement report deadline timer (measurement report timer) for the terminal device, and the configuration message includes a running time of the timer described in the embodiment of the present application.
  • the configuring side of the timer may be the source base station, or other network equipment that communicates with the terminal device, or configure the starting time and running time of the timer in advance by a preset method. This application does not address this. limited.
  • the length of the measurement report timer can be configured by using an RRC message, or the length of the measurement report timer is configured in a condition switching command.
  • a terminal device receives a conditional switching command, it starts a timer at the first time and sets the running time of the timer to the first time.
  • the first time may be the time when the switching command is received, or it may be another time.
  • the switch command can also be called a switch message.
  • the first candidate cell set here includes at least one candidate cell, and each candidate cell in the first candidate cell set may be a candidate cell determined by the terminal device according to a conditional switching request sent by the source base station, that is, in the first candidate cell set.
  • Each candidate cell may be a candidate cell that has been determined by the terminal device based on the condition switching method in the prior art.
  • the terminal device needs to select an optimal one from multiple candidate cells in the first candidate cell set that meets the conditions.
  • the cell is the target cell to be switched by the terminal device.
  • the terminal device cannot determine a handover target cell from a plurality of candidate cells according to the handover condition. Specifically, the terminal device cannot determine a handover target cell from a plurality of candidate cells according to the handover condition, that is, none of the plurality of candidate cells meet the current handover condition.
  • the terminal device determines the target cell for handover from a plurality of candidate cells according to the handover conditions included in the condition handover command, but from the first moment when the timer starts, the terminal device does not switch to
  • the terminal device may report a measurement report to the source base station after the preset time period (that is, the timer expires) from the moment when the terminal device obtains the handover condition.
  • the measurement report may include more A measurement report of a cell, that is, the measurement report is used to determine a second candidate cell set.
  • the content of the measurement report in the embodiments of the present application may be the signal reception quality or communication quality of the candidate cell or the channel transmission quality of the received signal.
  • reference signal received power RSRP
  • SINR signal noise interference ratio
  • RSRQ reference signal reception quality
  • SNR Signal-to-noise ratio
  • the second candidate cell set includes at least one cell that does not belong to the first candidate cell set, or the first candidate cell set includes at least one cell that does not belong to A cell of the second candidate cell set.
  • the second candidate cell set includes at least one new neighboring cell, that is, at least one of the M candidate cells is a new cell other than the first candidate cell set; or all of the second candidate cell set includes The new neighboring cells, that is, the M candidate cells determined by the source base station do not belong to the first candidate cell set. This application does not limit this.
  • the terminal device by adding a new neighbor cell to the candidate cell set, when the communication quality of the candidate cells included in the original first candidate cell set is not high, it can provide more options for the terminal device, such as increasing communication Higher quality cells, thereby ensuring that the terminal device can select a cell with better communication quality for handover, thereby ensuring that the terminal device can select a more suitable target cell, and ensuring the communication quality between the terminal device and the base station.
  • the cells included in the second candidate cell set are cells remaining after deleting multiple candidate cells in the first candidate cell set.
  • the terminal device starting a timer includes: the terminal device starting the timer according to a condition switching command received from a network device.
  • the above solution defines the time when the terminal device starts the timer.
  • the time when the timer is started may be the time when the terminal device receives the condition switching command sent by the source base station, or the time when the timer is started may be obtained by the terminal device.
  • the time of the handover condition in the condition handover command (that is, the time to complete the message parsing), or the time to start the timer is a preset time after the time when the terminal device receives the condition handover command sent by the source base station (also It can be the moment when a message is received).
  • the terminal device receives the condition switching command, there may be corresponding processing and response time. Therefore, the specific starting time of the timer is not limited in this application. For various possible starting times of the timer, It falls into the protection scope of this application.
  • the method further includes: the terminal device does not send the measurement report within a first duration of the timer operation.
  • the terminal device in order to limit the terminal device from sending a measurement report to the base station, the terminal device does not report the measurement report to the base station during the first period of operation of the timer. When the second duration expires, the terminal device reports a measurement report to the base station.
  • the method further includes: the terminal device acquires a first preset condition; and within a first period of time when the timer runs, when the first cell When the first preset condition is satisfied, and the time length that satisfies the first preset condition is greater than or equal to the second time duration, the terminal device sends the measurement report, and the second time duration is less than or equal to the first time duration, wherein the first A cell is a cell other than the first candidate cell set, and the first preset condition includes that the communication quality of the first cell is higher than a first quality threshold, or that the communication quality of the first cell is higher than all candidate cells.
  • the terminal device If a new candidate cell satisfies the newly defined measurement event, and the duration of the newly defined measurement event is greater than or equal to a preset second duration, the terminal device is in a period corresponding to the second duration of the timer from starting to running
  • the measurement result may also be reported to the source base station, and the source base station requests the handover of the terminal device from the new cell according to the measurement result.
  • a newly defined measurement event such as a P1 event
  • a new candidate cell within the operating time after the timer is started, thereby ensuring that the terminal device can select a cell with better communication quality for handover, thereby ensuring that the terminal device can select a more
  • a suitable target cell ensures the communication quality between the terminal device and the base station.
  • the information of the second candidate cell set received by the terminal device from the network device includes indication information of adding a cell to the first candidate cell list.
  • the information of the second candidate cell set that the terminal device receives from the network device includes instruction information for releasing cells in the first candidate cell list.
  • the terminal device by adjusting the candidate cell list of the terminal device, for example, performing addition and deletion of the candidate cell list, it is ensured that the terminal device can select a cell with better communication quality for handover, thereby ensuring that the terminal device can select a more suitable target cell. Ensure the communication quality between the terminal device and the base station.
  • the validity period of the pre-allocated random access resources can also be adjusted.
  • the base station can modify the resource configuration of the candidate cell.
  • the validity period of the pre-configured resource can be extended, or a newly configured effective resource can be provided.
  • the terminal device can efficiently access the candidate cell through the dedicated random access resource.
  • a cell handover method including: a network device sends a condition handover command; and when the terminal device does not determine a target cell to be handed over from the first candidate cell set outside the first duration
  • the network device receives a measurement report from the terminal device, and the measurement report is used to determine a second candidate cell set, and the first duration is a running time of the terminal device timer; the network device sends the second candidate cell set to the terminal device. information.
  • a timer can be set to prevent the terminal device from reporting the measurement of a cell with poor communication quality.
  • the base station does not need to receive measurement reports of cells with low communication quality, which reduces unnecessary signaling overhead.
  • a new candidate cell is reported within the operating time after the timer is started, to ensure that the terminal device can select a cell with better communication quality for handover.
  • the base station can adjust the candidate cell list of the terminal device, for example, add or delete some cells in the candidate cell list, or adjust the validity period of the pre-allocated random access resources of the candidate cell, thereby ensuring that the terminal device can switch to a more appropriate Target cell to ensure the communication quality between the base station and the terminal device.
  • the second candidate cell set includes at least one cell that does not belong to the first candidate cell set, or the first candidate cell set includes at least one cell that does not belong to the first A cell of two candidate cell sets.
  • condition switching command is used to trigger the terminal device to start a timer.
  • the method further includes: within a first duration of the timer running, when the first cell meets the first preset condition, and the first cell
  • the network device receives the terminal device to send the measurement report, and the second duration is less than or equal to the duration of the period during which the timer runs; the network device determines according to the measurement report The second candidate cell set; wherein the first cell is a cell other than the first candidate cell set, and the first preset condition includes that the communication quality of the first cell is higher than a first quality threshold, or the first cell The communication quality of the cell is higher than all candidate cells.
  • the information of the second candidate cell set includes indication information of adding a cell to the first candidate cell list.
  • the information of the second candidate cell set includes instruction information for releasing cells in the first candidate cell list.
  • the source base station sends information of the second candidate cell set to the terminal device, and the information of the second candidate cell set may include instruction information that the source base station adds a cell to the first candidate cell list, For example, target cell add modlist, which contains the index of candidate cells, cell identification information (such as frequency and physical cell identification ID), and cell configuration information.
  • target cell add modlist which contains the index of candidate cells
  • cell identification information such as frequency and physical cell identification ID
  • the terminal device determines information of a new neighbor cell to be added, and adds the candidate neighbor cell to the original first candidate cell set, thereby obtaining a second candidate cell set. .
  • the information of the second candidate cell set received by the terminal device from the source base station may include indication information that the source base station releases the cells in the first candidate cell list.
  • the condition handover command may include a target cell release list of a candidate cell.
  • the information in the list is an index of the candidate target cell, which indicates that the cell indicated by the index is deleted from the candidate target cell list.
  • the terminal device locally saves a candidate cell list var target cell list, and the addition or release operations in the condition switching command are directed to the content of the list stored locally by the terminal device.
  • the terminal device when the terminal device has not completed the condition switch for a long time, it is possible that the terminal device will send a measurement report to the base station under the condition of timer timeout or P1 event.
  • the base station can adjust the candidate cell list according to the latest measurement results and make corresponding Add or delete operations.
  • a device for cell switching including: a processing unit for starting a timer; a communication unit when the timer expires and the terminal device does not determine a target to be switched from the first candidate cell set In the case of a cell, it is used to send a measurement report to the network device, the measurement report is used to determine the second candidate cell set; the communication unit is further configured to receive the information of the second candidate cell set from the network device, and from the second candidate The target cell to be switched is determined in the cell set.
  • the second candidate cell set includes at least one cell that does not belong to the first candidate cell set, or the first candidate cell set includes at least one cell that does not belong to the first A cell of two candidate cell sets.
  • the processing unit is further configured to: the terminal device start the timer according to a condition switching command received from a network device.
  • the processing unit is further configured to: within a first duration of running the timer, determine to not send the measurement report.
  • the communication processing unit is further configured to: obtain a first preset condition; and, within the first duration of the timer running, the processing unit, when When the first cell satisfies the first preset condition, and the duration that satisfies the first preset condition is greater than or equal to the second duration, the first cell is used to send the measurement report, and the second duration is less than or equal to the first duration, where:
  • the first cell is a cell other than the first candidate cell set, and the first preset condition includes that the communication quality of the first cell is higher than a first quality threshold, or the communication quality of the first cell is higher than all candidate cells .
  • the information of the second candidate cell set includes indication information of adding a cell to the first candidate cell list.
  • the information of the second candidate cell set includes instruction information for releasing cells in the first candidate cell list.
  • an apparatus for cell switching including: a communication unit for sending a conditional switching command; the communication unit is outside the first time period, and the terminal device does not determine the In the case of the handover target cell, it is also used to receive a measurement report from the terminal device, the first duration is the operating time of the terminal device timer; a processing unit is used to determine a second candidate cell set based on the measurement report; The unit is further configured to send information of the second candidate cell set to the terminal device.
  • the second candidate cell set includes at least one cell that does not belong to the first candidate cell set, or the first candidate cell set includes at least one cell that does not belong to the first A cell of two candidate cell sets.
  • condition switching command is used to trigger the terminal device to start a timer.
  • the communication unit is further configured to: within a first duration of the timer running, when the first cell meets the first preset condition, and When the duration of the first preset condition is greater than or equal to the second duration, receiving the terminal device to send the measurement report, the second duration is less than or equal to the first duration of the timer operation; the processing unit is further configured to The report determines the second candidate cell set; wherein the first cell is a cell other than the first candidate cell set, and the first preset condition includes that the communication quality of the first cell is higher than a first quality threshold, or the The communication quality of the first cell is higher than all candidate cells.
  • the information of the second candidate cell set includes indication information of adding a cell to the first candidate cell list.
  • the information of the second candidate cell set includes instruction information for releasing cells in the first candidate cell list.
  • a cell switching method including: a terminal device acquiring a first switching condition and a second switching condition, the first switching condition and the second switching condition being used by the terminal device from a plurality of candidate cells Determine the target cell for handover; when each candidate cell in the plurality of candidate cells does not satisfy the first handover condition, and when the communication quality of the source cell in which the terminal device is located decreases, the wireless link of the terminal device fails , The terminal device determines a handover target cell from the plurality of candidate cells according to the second handover condition; or
  • the terminal device determines a target cell for handover from the at least two candidate cells according to the second handover condition.
  • the terminal device when at least two candidate cells of the plurality of candidate cells meet the first handover condition, the terminal device removes from the at least two according to the second handover condition. Determining a handover target cell in the candidate cells includes: when at least two candidate cells in the plurality of candidate cells satisfy the first handover condition, the terminal device determines handover from the plurality of candidate cells according to the second handover condition. Target cell.
  • the second handover condition further includes that the candidate cell that can be the target cell is in the first state for a period of time greater than or equal to the first period of time, the first state It is a state where the communication quality is higher than the first quality threshold.
  • the terminal device determines a target cell for handover from the plurality of candidate cells according to the second handover condition, or the terminal device performs the handover according to the second handover.
  • determining the target cell for handover from the at least two candidate cells includes: determining the at least multiple candidate cells or the candidate cell with the highest signal strength value among the at least two candidate cells as the target cell for handover; and / Or determining a handover target cell from among the multiple candidate cells or the at least two candidate cells according to a preset sequence number; and / or from the at least multiple candidate cells or the at least two according to a preset priority order Among the candidate cells, a target cell for handover is determined.
  • a cell handover method including: the source base station sends a first handover condition and a second handover condition to a terminal device, where the first handover condition and the second handover condition are used by the terminal device from a plurality of The target cell in the candidate cell is determined; the source base station receives a handover completion message sent by the target base station, the handover completion message is used to indicate that the terminal device has handed over to the target cell; wherein when each candidate in the plurality of candidate cells None of the cells satisfies the first handover condition, and when the wireless link of the terminal device fails due to a decrease in the communication quality of the source base station, the target cell is determined by the terminal device from the plurality of candidate cells according to the second handover condition. Or when at least two candidate cells in the plurality of candidate cells satisfy the first handover condition, the target cell is determined by the terminal device from the at least two candidate cells according to the second handover condition, the The target base station provides the target cell to the terminal device.
  • the second handover condition further includes that the candidate cell that can be the target cell is in the first state for a period of time greater than or equal to the first period of time, the first state It is a state where the communication quality is higher than the first quality threshold.
  • the target cell is the candidate cell with the highest signal strength value among the at least multiple candidate cells or the at least two candidate cells; and / or the target cell It is determined according to a preset sequence number among the at least multiple candidate cells or the at least two candidate cells; and / or the target cell is the at least multiple candidate cells or the at least two candidate cells according to a preset The priority order is determined.
  • an apparatus for cell handover including: an obtaining unit for obtaining a first handover condition and a second handover condition, the first handover condition and the second handover condition being used by the terminal device from a plurality of Determining a target cell for handover in a candidate cell; a determining unit, when each candidate cell in the plurality of candidate cells does not satisfy the first handover condition, and is used when the radio link fails due to a decrease in the communication quality of the source cell Determine a target cell for handover from the plurality of candidate cells according to the second handover condition; or when at least two candidate cells in the plurality of candidate cells meet the first handover condition, use the method according to the second handover condition , Determining a handover target cell from the at least two candidate cells.
  • the determining unit is further configured to: At least two candidate cells satisfy the first handover condition, and when the radio link fails due to a decrease in the communication quality of the source cell, a target cell for handover is determined from the plurality of candidate cells according to the second handover condition.
  • the second handover condition further includes that the candidate cell that can be the target cell is in the first state for a period of time greater than or equal to the first period of time, the first state It is a state where the communication quality is higher than the first quality threshold.
  • the determining unit is further configured to determine the candidate cell having the highest signal strength value among the at least multiple candidate cells or the at least two candidate cells as The target cell for handover; and / or determining the target cell for handover from the at least multiple candidate cells or the at least two candidate cells according to a preset sequence number; and / or from the at least multiple according to a preset priority order Among the candidate cells or the at least two candidate cells, a target cell for handover is determined.
  • an apparatus for cell switching including: a sending unit, configured to send a first switching condition and a second switching condition to a terminal device, where the first switching condition and the second switching condition are used for the terminal device Determining a target cell for handover from a plurality of candidate cells; a receiving unit for receiving a handover completion message sent by the target base station, the handover completion message is used to indicate that the terminal device has handed over to the target cell;
  • a sending unit configured to send a first switching condition and a second switching condition to a terminal device, where the first switching condition and the second switching condition are used for the terminal device Determining a target cell for handover from a plurality of candidate cells; a receiving unit for receiving a handover completion message sent by the target base station, the handover completion message is used to indicate that the terminal device has handed over to the target cell;
  • Each of the candidate cells does not satisfy the first handover condition, and when the wireless link of the terminal device fails due to a decrease in communication quality, the target cell is the terminal device from the plurality
  • the second handover condition further includes that a candidate cell that can be a target cell is in a first state for a period of time greater than or equal to the first period, and the first state is high communication quality. At the first quality threshold.
  • the target cell is the candidate cell with the highest signal strength value among the at least multiple candidate cells or the at least two candidate cells; and / or the target cell It is determined according to a preset sequence number among the at least multiple candidate cells or the at least two candidate cells; and / or the target cell is the at least multiple candidate cells or the at least two candidate cells according to a preset The priority order is determined.
  • a communication device has a function of implementing a terminal device in the method design of the first and fifth aspects described above.
  • These functions can be implemented by hardware, or they can be implemented by hardware executing corresponding software.
  • the hardware or software includes one or more units corresponding to the functions described above.
  • a communication device has a function of implementing a network device (for example, a base station) in the method design of the second and sixth aspects.
  • a network device for example, a base station
  • These functions can be realized by hardware, and can also be implemented by hardware executing corresponding software.
  • the hardware or software includes one or more units corresponding to the functions described above.
  • a terminal device including a transceiver and a processor.
  • the terminal device further includes a memory.
  • the processor is used to control the transceiver to send and receive signals
  • the memory is used to store a computer program
  • the processor is used to call and run the computer program from the memory, so that the terminal device executes the foregoing first aspect or any one of the first aspect.
  • a network device including a transceiver and a processor.
  • the network device further includes a memory.
  • the processor is used to control the transceiver to send and receive signals
  • the memory is used to store a computer program
  • the processor is used to call and run the computer program from the memory, so that the terminal device executes the second aspect or any one of the second aspect.
  • a communication system which includes the terminal device of the third aspect and the terminal device of the seventh aspect; or the system includes the network device of the fourth aspect and the network device of the eighth aspect.
  • a communication device may be a terminal device designed in the foregoing method, or a chip provided in the terminal device.
  • the communication device includes a processor coupled to the memory, and may be configured to execute instructions in the memory to implement the foregoing first aspect or any possible implementation manner of the first aspect, and the foregoing fifth aspect or any one of the fifth aspect.
  • the communication device further includes a memory.
  • the communication device further includes a communication interface, and the processor is coupled to the communication interface.
  • the communication interface may be a transceiver, or an input / output interface.
  • the communication interface may be an input / output interface.
  • the transceiver may be a transceiver circuit.
  • the input / output interface may be an input / output circuit.
  • a communication device may be a network device in the foregoing method design, or a chip provided in the network device.
  • the communication device includes a processor coupled to the memory, and may be configured to execute instructions in the memory to implement the second aspect or any possible implementation manner of the second aspect, and the sixth aspect or any of the sixth aspect. Method implemented by a network device in a possible implementation.
  • the communication device further includes a memory.
  • the communication device further includes a communication interface, and the processor is coupled to the communication interface.
  • the communication interface may be a transceiver, or an input / output interface.
  • the communication interface may be an input / output interface.
  • the transceiver may be a transceiver circuit.
  • the input / output interface may be an input / output circuit.
  • a computer program product includes: computer program code that, when the computer program code runs on a computer, causes the computer to execute the methods in the above aspects.
  • a computer-readable medium stores program code, and when the computer program code runs on a computer, the computer causes the computer to execute the methods in the foregoing aspects.
  • FIG. 1 is a schematic structural diagram of a mobile communication system applicable to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a process in which a terminal device implements a handover from a source base station to a target base station.
  • FIG. 3 is a schematic interaction diagram of a condition switching technology.
  • FIG. 4 is a schematic interaction diagram of an example of a method for conditional switching provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a trigger switching of a measurement event according to an embodiment of the present application.
  • FIG. 6 is a schematic interaction diagram of an example method 600 for conditional switching according to an embodiment of the present application.
  • FIG. 7 is a schematic diagram of an example measurement event provided by an embodiment of the present application.
  • FIG. 8 is a schematic block diagram of an example communication device according to an embodiment of the present application.
  • FIG. 9 is a schematic block diagram of another example communication device according to an embodiment of the present application.
  • FIG. 10 is a schematic block diagram of another example communication device according to an embodiment of the present application.
  • FIG. 11 is a schematic block diagram of another example communication device according to an embodiment of the present application.
  • FIG. 12 is a schematic diagram of an example communication device according to an embodiment of the present application.
  • FIG. 13 is a schematic diagram of another example communication device according to an embodiment of the present application.
  • LTE long term evolution
  • FDD frequency division duplex
  • LTE time division duplex LTE time division duplex
  • 5G 5th generation
  • NR new wireless
  • FIG. 1 shows a communication system 100 applied in an embodiment of the present application.
  • the communication system 100 may include at least two wireless access network devices (for example, the network device 110 and the network device 120) and a terminal device (for example, the terminal device 130).
  • the terminal device is connected to the wireless access network device in a wireless manner, and the wireless access network device is connected to the core network device in a wireless or wired manner.
  • the core network equipment is not shown in Figure 1. It should be understood that the core network equipment and the radio access network equipment may be separate and different physical devices, or the functions of the core network equipment and the radio access network equipment are logical functions. Integrated on the same physical device, it can also be a physical device that integrates some core network device functions and some wireless access network device functions.
  • the terminal equipment can be fixed or removable.
  • FIG. 1 is only a schematic diagram, and the communication system may further include other network devices, such as a wireless relay device and a wireless backhaul device, which are not shown in FIG. 1.
  • the embodiments of the present application do not limit the number of core network devices, radio access network devices, and terminal devices included in the mobile communication system.
  • the radio access network device 120 is an access device that the terminal device accesses to the mobile communication system by wireless.
  • the radio access network device 120 may be: a base station, an evolved base station (eNB), a home base station, an access point (AP) in a wireless fidelity (WIFI) system, and A relay node, a wireless backhaul node, a transmission point (TP), or a transmission and reception point (TRP), etc., can also be a gNB in an NR system, or it can be a component or part of a base station Equipment, such as a central unit (CU), a distributed unit (DU), or a baseband unit (BBU).
  • CU central unit
  • DU distributed unit
  • BBU baseband unit
  • the wireless access network device is referred to as a network device.
  • the network device refers to a wireless access network device.
  • the network device 110 and the network device 120 may be devices that communicate with terminal devices. Each network device may provide communication coverage for a specific geographic area, and may communicate with terminal devices located in the coverage area (cell).
  • the network device may refer to the network device itself, or a chip applied to the network device to perform a wireless communication processing function.
  • an access network device provides services to a cell
  • a terminal device communicates with the access network device through a transmission resource (for example, a frequency domain resource or a spectrum resource) used by the cell.
  • a transmission resource for example, a frequency domain resource or a spectrum resource
  • It may be a cell corresponding to an access network device (such as a base station), and the cell may belong to a macro base station or a small cell.
  • the small cell here may include: a metro cell, a micro cell ( micro cells, pico cells, femto cells, etc. These small cells have the characteristics of small coverage and low transmission power, and are suitable for providing high-rate data transmission services.
  • the terminal equipment in the mobile communication system 100 may also be referred to as a terminal, a terminal device, a user equipment (UE), a mobile station (MS), a mobile terminal (MT), and the like.
  • the terminal device in the embodiment of the present application may be a mobile phone, a tablet, a computer with a wireless transmitting and receiving function, or a virtual reality (VR), augmented reality (AR) ), Industrial control (industrial control), driverless (self driving), remote medical (remote medical), smart grid (grid), transportation safety (transportation safety), smart city (smart city) and smart home (smart home) ) And other scenarios.
  • the foregoing terminal devices and chips applicable to the foregoing terminal devices are collectively referred to as terminal devices. It should be understood that the embodiment of the present application does not limit the specific technology and specific device form used by the terminal device.
  • FIG. 1 exemplarily shows two network devices and one terminal device.
  • the communication system 100 may include multiple network devices and the coverage of each network device may include other numbers of terminal devices. The embodiment does not limit this.
  • the wireless communication system 100 may further include other network entities such as a network controller, a mobility management entity, and the embodiment of the present application is not limited thereto.
  • the handover of the terminal device 130 from the source base station to the target base station will be taken as an example for description.
  • the source base station and the target base station here may be one base station, that is, the terminal device 130 switches between two different cells under the same base station; or the source base station and the target base station may be two different base stations, that is, the terminal The device 130 switches between two different cells under two base stations. As shown in FIG.
  • the terminal device 130 in the source base station 110 can switch from the source cell 1 to the target cell 2 under the source base station 110 to implement handover of different cells under the same base station 110 (different cells in the figure pass different Beam signal transmission); can also switch from the source base station 110 to the target base station 120, as shown in Figure 1, the handover of the source cell 1 to the target cell 3, to achieve different cell switching under different base stations.
  • the handover is performed in units of cells. Whether the source cell and the target cell are located in the same base station is not limited in this application.
  • the terminal device 130 will be mainly described in detail as an example for handover from the source base station to the target base station.
  • FIG. 2 is a schematic diagram of a process in which a terminal device implements a handover from a source base station to a target base station. As shown in FIG. 2, the cell handover process specifically includes the following four stages.
  • the measurement control phase includes steps 1 to 2 in FIG. 2.
  • the terminal device initially communicates with the source base station, and the source base station sends measurement control information to the terminal. After receiving the measurement control information, the terminal device performs measurement based on the measurement control information. When the measurement report reporting conditions are met, the terminal device reports the measurement result to the source base station.
  • the source base station executes a measurement control program according to the operating characteristics and location characteristics of the terminal device, and requires the terminal device to provide a corresponding measurement report in the form of an event trigger or a periodic report for the source base station to make a decision to trigger a handover.
  • the handover preparation phase includes steps 3 to 7 in Figure 2.
  • the source base station After the source base station receives the measurement results sent back by the terminal device, it performs a handover decision based on the measurement results reported by the terminal.
  • the source base station can determine the service quality of the terminal device's services and surrounding wireless resources. Perform handover selection in such cases, determine the target base station for the handover of the terminal device, and send a handover request message (handover request, HO request) to the target base station.
  • handover request handover request, HO request
  • the target base station After the target base station receives the HO request, it detects the basic attributes, wireless parameters, and measurement results of the terminal equipment carried by the signaling.
  • the target base station performs admission control, determines the receiving terminal equipment, and then sends a handover request response message (handover request acknowledgement, HOreq (ACK) signaling to the source base station, and then the source base station sends a radio resource control (radio resource control (RRC) connection reconfiguration message), that is, a handover command to the terminal device, marking the completion of the handover preparation work.
  • a handover request response message handover request acknowledgement, HOreq (ACK) signaling to the source base station
  • RRC radio resource control
  • the RRC message handover command also contains information to be provided to the terminal device, including the new cell wireless network temporary network identifier (C-RNTI), random access channel information, and system information block (system information block). information, block (SIB), etc., can help the terminal get in touch with the target base station in the shortest time and resume communication.
  • C-RNTI new cell wireless network temporary network identifier
  • SIB system information block
  • SIB block
  • the handover execution phase includes steps 7 to 11 in FIG. 2.
  • the terminal device accesses the target base station according to the parameters carried in the handover command.
  • the terminal device disconnects the connection with the source base station, sends a random access request to the target base station, and requests it to provide a TA adjustment value to complete uplink synchronization.
  • the source base station sends the downlink data to the target base station in a buffer mode; after the link is established, it is then delivered to the terminal device to ensure no data loss.
  • the target base station detects the request from the terminal device within the random access cycle, sends confirmation signaling of the random access request to the terminal, allocates uplink resources, and responds to the TA adjustment value to help the terminal device synchronize the connection after receiving this confirmation signaling.
  • the terminal device sends handover completion signaling to the target base station to complete synchronization with the target base station, marking that the handover execution is successfully completed, and the terminal device and the target base station resume normal communication.
  • the handover completion phase includes steps 12 to 18 in FIG. 2.
  • the target base station sends a path switching request to the access gateway, requesting to change the downlink data path of the terminal device and update the user interface.
  • the access gateway After the access gateway completes, it sends an end marker signaling to the source base station to mark the end of the buffered data, and notifies the target base station that the update is complete.
  • the target base station then notifies the source base station that the handover is complete and lets it release system resources occupied by the terminal.
  • the source base station sends buffered data until it encounters the end marker flag.
  • the terminal device can switch the serving cell according to the change in signal strength.
  • the terminal device receives the handover command, the terminal The device disconnects the RRC connection with the source base station, and then starts the random access process for the target base station. After sending the handover completion message to the target base station in step 11, the terminal device resumes the RRC connection. It can be known that, from step 7 to step 11, the data transmission of the terminal device is interrupted during this handover process.
  • FIG. 3 is a schematic interaction diagram of a condition switching technology. As shown in FIG. 3, FIG. 3 includes steps from S301 to S310, and the details are as follows:
  • the terminal device sends a measurement report to the source base station.
  • the source base station makes an early handover decision according to the measurement report reported by the terminal device, that is, the source base station determines multiple target base stations that need to send a handover request.
  • the source base station sends a handover request message to multiple target base stations, which is used to request access of the terminal device from the multiple target base stations;
  • the target base station performs admission control according to the received handover request message.
  • the target base station After the target base station determines to receive the terminal device, it sends a handover request response message to the source base station to notify the source base station to grant access to the terminal device;
  • the source base station sends a handover command to the terminal device.
  • the handover command includes a handover condition, and the handover command can indicate multiple candidate cells;
  • the terminal device receives a handover command sent by the source cell and evaluates the handover condition to select a target cell for the new handover.
  • the terminal device When it is determined that the target cell meets the handover condition, the terminal device performs downlink synchronization and random access with the target base station;
  • the terminal device sends a handover confirmation message to the target base station.
  • the target base station sends a handover completion message to the terminal device to complete the entire handover process.
  • conditional handover process 300 the main difference between the conditional handover technology and the traditional cell handover is that the source base station indicates multiple candidate target cells to the terminal device in the handover command, and the corresponding handover conditions.
  • the terminal device keeps the connection with the source base station on the one hand, and evaluates the handover conditions on the other hand.
  • the terminal device starts the downlink synchronization and random access process with the cell, and sends a handover completion message to complete the handover.
  • FIG. 3 shows only one target base station for the sake of brevity. However, during the actual handover preparation process, the source base station will communicate with multiple candidate base stations.
  • the source base station will perform a handover command. Indicates to the terminal device as a candidate base station for the terminal device.
  • the time point of the switching is determined by the terminal device itself, which avoids the problem of sending the switching command too early or too late, and improves the robustness of the switching.
  • a terminal device receives a conditional handover command sent by a source base station, it starts to evaluate whether the measurement conditions of multiple candidate cells meet the handover condition according to the conditional handover command, that is, select a target cell whose signal strength meets the handover condition from multiple candidate cells. .
  • the terminal device cannot determine the target cell according to the existing conditional switching command, the terminal device needs to continue to wait.
  • this application proposes a handover method, which mainly improves the conditional handover method, provides a method for processing terminal equipment and base stations in abnormal scenarios, and provides a way for terminal equipment and source base stations to end communication and explicitly stop. Time point of data transmission to avoid wasting resources.
  • FIG. 4 is a schematic interaction diagram of an example method 400 for conditional switching according to an embodiment of the present application. Each step of the method 400 is described in detail below. As shown in FIG. 4, during the cell handover process, the terminal device may execute the method 400 shown in FIG. 4.
  • the terminal device and the base station are taken as the execution subjects of the execution method 400 as an example to describe the method 400.
  • the execution subject of the execution method 400 may also be a chip applied to a terminal device and a chip applied to a base station, and therefore, they are collectively referred to as a terminal device.
  • the method 400 specifically includes the following.
  • the terminal device obtains a first handover condition and a second handover condition, and the first handover condition and the second handover condition are used by the terminal device to determine a handover target cell from a plurality of candidate cells.
  • the target cell to be switched by the terminal device may be understood as at least one candidate cell that meets the current handover condition of the terminal device.
  • the candidate cell may be a terminal device that has been determined based on the condition switching method in the prior art. After determining multiple candidate cells, the terminal device may use the condition switching method provided in the embodiment of the present application for selection. Among the candidate target cells, an optimal cell is selected as a target cell to be switched by the terminal device.
  • the terminal device when determining that there are currently no target cells that meet the existing handover conditions, the terminal device needs to select a cell with the best current signal strength from these target cells.
  • the multiple candidate cells may also be multiple candidate cells that do not meet the existing handover conditions. This application does not limit whether the multiple candidate target cells meet the existing conditional handover technologies.
  • the terminal device if the terminal device receives the conditional switching command sent by the base station, the terminal device enters the evaluation state, that is, the terminal device has not completed the handover. If the signal strength of the source base station or the source cell suddenly decreases poorly, the terminal device may cause a radio link failure (RLF) due to the sudden decrease of the signal strength of the source cell, or if the multiple candidate cells and the source cell Both are a cell within the range of the base station, so the signal strength of the source cell and the candidate cell will decrease at the same time because the signal strength of the base station is reduced. At this time, the wireless link of the terminal device will also fail. The terminal device must choose a target cell Connect now.
  • RLF radio link failure
  • the cell switching method provided in the embodiment of the present application can be used to perform timely cell switching to avoid normal communication of the terminal device in various abnormal scenarios.
  • the embodiment of the present application does not limit the manner, acquisition timing, and acquisition sequence of the terminal device acquiring the first switching condition and the second switching condition.
  • the first handover condition may be a handover condition in an existing condition handover method, and the terminal device may determine a target cell to be handed over from a plurality of candidate cells according to the condition handover command. In other words, the terminal device is based on the first handover condition. Information to determine the target cell for handover from multiple candidate cells.
  • the second switching condition may be a newly added switching condition in this application.
  • the first handover condition includes that the communication quality of a candidate cell that can be used as the target cell needs to be higher than a second quality threshold; the second condition includes that the communication quality of a candidate cell that can be used as the target cell needs Above the third quality threshold.
  • the second handover condition may be a handover condition pre-configured to the terminal device, or the information of the second handover condition may be both information about the first handover condition and the first handover condition are included in a condition handover command sent by the source base station to the terminal device.
  • the pre-configuration may be pre-configured through a radio resource control (radio resource control (RRC) message), or a well-known condition and a correspondence relationship between each candidate cell.
  • RRC radio resource control
  • the source base station sends a condition switching command to the terminal device, and the terminal device enters an evaluation state after receiving the condition switching command.
  • the terminal device determines a target cell according to the first handover condition and the second handover condition.
  • the terminal device receives a conditional handover command sent by the source base station, and the source base station indicates multiple candidate cells to the terminal device through the conditional handover command.
  • the multiple candidate cells are the source base station and the target base station providing the target cell for the terminal device.
  • the cell to which the terminal device switches in can be accepted.
  • the terminal device determines a plurality of candidate cells, the terminal device collectively selects a target cell from the plurality of candidate cells according to the first handover condition. Specifically, the following scenarios are included:
  • the terminal device When each candidate cell of the plurality of candidate cells does not satisfy the first handover condition, and when the communication quality of the source cell where the terminal device is located causes the wireless link of the terminal device to fail, the terminal device is based on the The second handover condition determines a handover target cell from the plurality of candidate cells.
  • the terminal device determines, from among multiple candidate cells, that the communication quality of each candidate cell does not meet the communication quality requirements included in the first handover condition.
  • the first handover condition may include a threshold of communication quality. When the communication quality of the plurality of candidate cells is less than the communication quality threshold, it may be considered that each candidate cell of the plurality of candidate cells does not satisfy the first Switching conditions.
  • the terminal device still needs to select an optimal cell from the multiple candidate cells in time as the target cell, and understand to switch to the target cell.
  • the source base station may set the same handover condition for multiple candidate cells, or may set different handover conditions.
  • the switching condition may be based on an existing measurement event, such as an A3 event.
  • the entry condition of the A3 event is that the signal strength of the target cell is higher than the offset of the source cell.
  • the entry conditions for the A3 event can be expressed as equation (1).
  • Mn is the measurement result of the neighboring cell, the corresponding offset value of the Ofn neighboring cell frequency, the related offset value of the Ocn neighboring cell, the measurement result of the Mp source cell, the corresponding offset value of the Ofp source cell frequency, and Ocp is the corresponding offset of the source cell Shift value, Hys is the hysteresis value, Off is the offset value corresponding to the event.
  • Ocn, Ofp, Ocp, Hys, Off are all values representing relative values, which are all configured by the source base station to the terminal device, and the units can all be dB.
  • Mn and Mp are the results measured by the terminal device.
  • the cell measurement results can be reference signal received power (RSRP), signal to interference plus noise ratio (SINR), or reference signal reception. Quality (reference, quality, RSRQ).
  • RSRP reference signal received power
  • SINR signal to interference plus noise ratio
  • RSRQ reference signal reception.
  • the unit of RSRP is milliwatt decibel (decibel referred to one milliWatt, dBm); when the neighbor measurement result Mn and the source cell measurement result Mp are both SINR
  • the unit of the SINR or RSRQ may be dB.
  • the first switching condition may include a measurement event described above, such as an A3 event; and the second switching condition may also include an existing measurement event, such as an A3 event.
  • the terminal device determines a target cell for handover from the at least two candidate cells according to the second handover condition.
  • the terminal The device determines a target cell for handover from the plurality of candidate cells according to the second handover condition.
  • the terminal device when the terminal device has determined, based on the first handover condition, that at least two candidate cells from multiple candidate cells both meet the first handover condition, the terminal device further needs to further select from the at least two candidate cells.
  • a target cell is selected for handover, that is, an optimal cell is selected from a plurality of candidate target cells that meet the conditions as a target cell to be switched by the terminal device.
  • the terminal device may select according to the second switching condition, and the communication quality threshold included in the second switching condition may be higher than the communication quality threshold included in the first switching condition. Therefore, the terminal device can determine an optimal candidate cell as the target cell.
  • the second handover condition may further include that the candidate cell that can be the target cell is in a first state for a time greater than or equal to a preset time period T ′, and the first state is communication quality A state above the first quality threshold.
  • a trigger switching diagram of the measurement event is shown.
  • the communication quality of the candidate cell is greater than the first quality threshold, and from the time T1 starts, within a preset time period T ′ (time-to-trigger), that is, the time T1 has passed a preset time period T ′
  • the terminal device may determine the candidate cell as the target cell for handover. Subsequently, the terminal device initiates a random access procedure for the cell, and then the target base station may send a handover completion message.
  • the source base station can configure the same set of measurement event parameters for each candidate cell, that is, a set of parameters is applicable to all candidate target cells, or different parameters are individually configured for each candidate cell, and some parameters can be configured as public Parameters, some of which are cell-specific parameters.
  • the parameters that may be configured are as shown in the above formula (1), including: frequency-dependent offset value, cell-related offset value, offset value, hysteresis value, time-to-trigger value, etc.
  • the source base station can adjust the probability that the terminal device accesses a certain cell, for example, a shorter time-to-trigger value will be used to make the terminal device access the corresponding cell faster.
  • the terminal device determines a target cell for handover from the plurality of candidate cells according to the second handover condition, or the terminal device selects from the at least two candidate cells according to the second handover condition.
  • the target cell for handover you can determine the target cell in the following ways.
  • the at least multiple candidate cells or the candidate cell with the highest signal strength value among the at least two candidate cells is determined as a target cell for handover.
  • a target cell for handover is determined from the at least multiple candidate cells or the at least two candidate cells according to a preset sequence number.
  • the candidate cell with the highest ranking is selected for handover.
  • the ranking can be the serial number of each cell in the candidate cell list, or a serial number configured separately. For example, a candidate cell with a rank of 1, 2, 3, and 10 is selected. After the first handover condition is determined, the cell serial number is 1, 3, 5, 7, 9, and the highest or smallest serial number can be selected according to the serial number. This application is not limited to this.
  • a target cell for handover is determined from the at least multiple candidate cells or the at least two candidate cells according to a preset priority order.
  • a cell with a higher priority is selected for handover. If the priorities are the same, the cell with the highest signal strength is selected for handover.
  • the terminal device does not switch to a new cell
  • the source cell fails due to a sudden decrease in signal strength.
  • the terminal device does not trigger the RRC connection re-establishment process, but executes immediately. Switch.
  • the signal strength of multiple candidate cells may also decrease, so an additional threshold needs to be designed to assist. Only cells with signal strength exceeding the threshold can be used as candidate target cells. If at least two candidate cells are selected, for further selection methods, reference may be made to any one of the above three methods.
  • the terminal device After the terminal device determines the target cell, it performs handover immediately.
  • the terminal device When the terminal device does not find a target cell that satisfies the first handover condition among multiple candidate cells according to the first handover condition in the condition handover command, the terminal device needs to continue to wait for the condition that a candidate cell meets the first handover condition. A switching condition, if it is satisfied, the switching is performed immediately.
  • the cell handover method provided by the foregoing embodiment includes combining the first handover condition in the existing conditional handover technology.
  • the cell switching method provided in the present application is used to determine a target cell from a plurality of candidate cells that do not satisfy the first switching condition by using a new switching condition, that is, a second switching condition.
  • the selection threshold setting of the candidate target cell was performed to prevent the terminal device from switching to a cell of poor quality and to ensure the communication quality.
  • the terminal device After receiving the condition switching command sent by the source base station, the terminal device enters an evaluation state and starts to evaluate whether the switching condition is satisfied. If the cell handover cannot be completed for a long time, how the terminal device selects a new and more reasonable target cell has no related solution in the prior art.
  • a cell switching method for a terminal device and a base station in this abnormal scenario will be described below.
  • a timer can be set to prevent the terminal device from reporting a measurement report of a cell with poor communication quality. And by adjusting the candidate cell list, the terminal device is provided with a more reasonable target cell, ensuring the accuracy of cell switching, and the communication between the terminal device and the base station.
  • FIG. 6 is a schematic interaction diagram of an example method 600 for conditional switching according to an embodiment of the present application. Each step of the method 600 is described in detail below. As shown in FIG. 6, during the cell handover process, the terminal device may execute the method 600 shown in FIG. 6.
  • the method 600 is described by taking a terminal device and a base station as an execution subject of the execution method 600 as an example.
  • the execution body of the execution method 600 may also be a chip applied to a terminal device and a chip applied to a base station.
  • the method 600 specifically includes the following.
  • the terminal device receives a condition switching command from a source base station.
  • the source base station sends a condition switching command to the terminal device.
  • the condition command may include a switching condition, and the terminal device enters an evaluation state after receiving the condition switching command.
  • the handover condition included in the condition handover command may be a handover condition in the prior art, for example, the first handover condition introduced in the cell handover method 400, which is not limited in this embodiment of the present application.
  • S602 The terminal device starts a timer.
  • the timer may be an expiration timer configured for the terminal device.
  • the source base station may configure a measurement report deadline timer (measurement report timer) for the terminal device, and the configuration message includes a running time of the timer mentioned in the embodiment of the present application.
  • the configuration side of the timer may be the source base station, or other equipment that communicates with the terminal device, or the startup time and running time of the timer are configured in advance by preset, which is not limited in this application.
  • the length of the measurement report timer can be configured by using an RRC message, or the length of the measurement report timer is configured in a condition switching command. If the terminal device starts the timer at the first moment after receiving the condition switching command, it is assumed that the running time of the timer is the first duration.
  • the terminal device starts the timer according to a condition switching command received from the network device.
  • the first time may be the time when the terminal device receives the conditional switching command sent by the source base station, or the first time may be the time when the terminal device acquires the switching condition in the conditional switching command (that is, the time when the message parsing is completed), Alternatively, the first time is a preset time (or a time when a message is received) after the time when the terminal device receives the conditional switching command sent by the source base station. It should be understood that when the terminal device receives the condition switching command, there may be corresponding processing and response time. Therefore, the specific starting time of the timer is not limited in this application. For various possible starting times of the timer, It falls into the protection scope of this application.
  • the terminal device does not send the measurement report to the source base station during the first duration of the timer operation.
  • the terminal device in order to limit the terminal device from sending a measurement report to the base station, the terminal device does not report the measurement report to the base station during the first period of operation of the timer. When the second duration expires, the terminal device reports a measurement report to the base station.
  • the terminal device determines that the timer expires, and the terminal device does not determine the target cell to be handed over from the first candidate cell set.
  • the terminal device sends a measurement report to the source base station, where the measurement report is used to determine a second candidate cell set.
  • the first candidate cell set here includes at least one candidate cell, and each candidate cell in the first candidate cell set may be a candidate cell determined by the terminal device according to a conditional switching request sent by the source base station, that is, in the first candidate cell set.
  • Each candidate cell may be a candidate cell that has been determined by the terminal device based on the condition switching method in the prior art.
  • the terminal device needs to select an optimal one from multiple candidate cells in the first candidate cell set that meets the conditions.
  • the cell is the target cell to be switched by the terminal device.
  • the terminal device cannot determine a handover target cell from a plurality of candidate cells according to the handover condition. Specifically, the terminal device cannot determine a handover target cell from a plurality of candidate cells according to the handover condition, that is, none of the plurality of candidate cells meet the current handover condition.
  • the terminal device determines the target cell for handover from a plurality of candidate cells according to the handover conditions included in the condition handover command, but from the first moment when the timer starts, the terminal device does not switch to
  • the terminal device may report a measurement report to the source base station after the preset time period from the moment when the terminal device obtains the handover condition, and the measurement report may include measurement reports of more other cells, that is, The measurement report is used to determine a second candidate cell set.
  • the terminal device measures N cells and reports the measurement report to the source base station.
  • the source base station selects M cells with better communication quality from the N cells as candidate cells according to the measurement reports of the N cells received, that is, M cells constitute the second candidate cell set described in the embodiment of the present application, where N is an integer greater than or equal to M, and M is a positive integer greater than or equal to 1.
  • the process of the source base station determining the candidate cell according to the measurement report reported by the terminal device may refer to the solution of the prior art or the related description of the cell switching method 400 of the foregoing embodiment, which is not repeated here.
  • the measurement report content in the embodiments of the present application may be the signal reception quality or communication quality of a candidate cell or a neighboring cell, or the channel transmission quality of a received signal.
  • RSRP reference signal received power
  • SINR signal noise interference ratio
  • RSRQ reference signal reception quality
  • SNR Signal to noise ratio
  • the second candidate cell set includes at least one cell that does not belong to the first candidate cell set, or the first candidate cell set includes at least one cell that does not belong to the second candidate cell set.
  • the second candidate cell set includes at least one new neighboring cell, that is, at least one of the M candidate cells is a new cell other than the first candidate cell set; or all of the second candidate cell set includes The new neighboring cells, that is, the M candidate cells determined by the source base station do not belong to the first candidate cell set. This application does not limit this.
  • the cells included in the second candidate cell set are cells remaining after deleting multiple candidate cells in the first candidate cell set.
  • the terminal device may obtain a first preset condition, and within a first period of time when the timer runs, when the first cell meets the first preset condition, and When the duration that satisfies the first preset condition is greater than or equal to the second duration, the terminal device sends the measurement report, and the second duration is less than or equal to the first duration.
  • the first cell is a cell other than the first candidate cell set, and the first preset condition includes that the communication quality of the first cell is higher than a first quality threshold, or that the communication quality of the first cell is higher than all Candidate cell.
  • the terminal device may also design a new measurement event according to the existing switching conditions, such as the existing measurement events in S401 and S402, such as the A3 event.
  • the existing switching conditions such as the existing measurement events in S401 and S402, such as the A3 event.
  • the details of the new measurement event will be described below. Application, name the event P1.
  • FIG. 7 is a schematic diagram of an example measurement event provided by an embodiment of the present application.
  • a new measurement event P1 as an example, when the entry condition of the new event P1 is satisfied and the duration of the entry condition of P1 exceeds a preset second time-to-trriger, that is, from time T3,
  • the new target cell satisfies the P1 event and the duration of the P1 event is greater than or equal to the second duration, that is, the duration represented by the period from T3 to T4.
  • the terminal device can report a measurement report to the base station.
  • the time T3 here is not necessarily related to the first time when the timer is started, and the time T3 may be a time before the first time or a time after the first time.
  • the measurement report is not reported; when the entry condition of the new event P1 is satisfied and the entry condition of P1 is exceeded for a preset period of time
  • the second duration time-to-trriger
  • the P1 event can be reported.
  • the entry condition of the P1 event may be that the signal strength of a cell is higher than a preset offset value of all candidate target cells, and the cell is not in the candidate target cell list.
  • the entry condition of the new measurement event P1 can be expressed as the following formula (2):
  • Mci is the signal strength of the candidate target cell with index number i
  • other parameters are defined by referring to the parameters and definitions described in the entry condition formula (1) of the A3 event.
  • the offset value Off may be set to 0, and if the offset Off is set to 0, the Off term may be canceled in the formula.
  • the terminal device may also report to the source base station during the period corresponding to the second duration of the timer from starting to running. The measurement result is reported, and the source base station requests the handover of the terminal device from the new cell according to the measurement result.
  • the terminal device receives information of the second candidate cell set from the source base station.
  • the terminal device If the terminal device cannot select a target cell from a plurality of candidate cells according to the existing handover conditions, the terminal device reports the latest to the source base station after the timer runs for the first duration (that is, the timer expires). The measurement results of the plot. When the terminal device reports the measurement report to the base station, the base station may adjust the candidate target cell list according to the corresponding measurement result.
  • the source base station After the source base station receives the measurement report sent by the terminal device, as described above, the measurement reports of N cells are reported, and M candidate cells are determined according to the measurement reports of the N cells, and the M candidate cells form the second candidate cell set.
  • the source base station sends the information of the second candidate cell set to the terminal device. After receiving the information of the second candidate cell set, the terminal device can obtain the information of the M candidate cells.
  • the information of the second candidate cell set or the information of the M candidate cells may include an index of M and candidate cells, cell identification information (such as frequency and physical cell identification ID), and cell configuration information.
  • cell identification information such as frequency and physical cell identification ID
  • cell configuration information such as cell configuration information.
  • the terminal device determines a target cell to be switched from the second candidate cell set.
  • the source base station may send the information of the M candidate cells to the terminal device.
  • the information of the M candidate cells may be included in the conditional handover command.
  • the terminal device may determine the M candidate cells. The terminal device then determines a target cell to be switched from the M candidate cells according to the switching conditions in the condition switching command, and then the terminal device can switch to the target cell to complete the entire cell switching process.
  • the source base station sends information of the second candidate cell set to the terminal device, and the information of the second candidate cell set may include instruction information that the source base station adds a cell to the first candidate cell list, For example, target cell add modlist, which contains the index of candidate cells, cell identification information (such as frequency and physical cell identification ID), and cell configuration information.
  • target cell add modlist which contains the index of candidate cells
  • cell identification information such as frequency and physical cell identification ID
  • the terminal device determines information of a new neighbor cell to be added, and adds the candidate neighbor cell to the original first candidate cell set, thereby obtaining a second candidate cell set. .
  • the information of the second candidate cell set received by the terminal device from the source base station may include indication information that the source base station releases the cells in the first candidate cell list.
  • a cell release list of a candidate cell may be included in the condition handover command.
  • the information in the list is an index of the candidate target cell, which indicates that the cell indicated by the index is deleted from the candidate target cell list.
  • the terminal device locally saves a candidate cell list var target cell list, and the addition or release operations in the condition switching command are directed to the content of the list stored locally by the terminal device.
  • the terminal device when the terminal device has not completed the condition switch for a long time, it is possible that the terminal device will send a measurement report to the base station under the condition of timer timeout or P1 event.
  • the base station can adjust the candidate cell list according to the latest measurement results and make corresponding Add or delete operations.
  • each cell provides configuration information for the terminal device, which may include dedicated random access resource indication information, and the terminal device may determine the communicable random access process based on the resource indication information. Resources.
  • a dedicated random access resource indication is included in the rach-config dedicated IC, which specifically indicates the use of a random access preamble index and time domain location information.
  • This resource is a resource that is allocated separately for the terminal device. On this basis, an effective time limit can be added to the dedicated resource to avoid resource waste caused by the terminal device not switching for a long time.
  • the embodiment of the present application also provides another scenario for modifying the first candidate cell list.
  • the resource configuration of the candidate cell can be modified, for example, the validity period of a pre-configured resource can be extended, or a newly configured effective resource can be provided. .
  • the effective time limit can be implemented in the following ways:
  • the valid time limit can be set to a valid duration, such as a third duration. Starting from the time T0 at which the terminal device receives the condition switching command, and the duration of the resource validity period is set to t, then from time T0, the period corresponding to T0 + t is the valid duration.
  • the dedicated random access resource allocated in advance after the time corresponding to T0 + t fails.
  • a timer can be set, for example, called a validity timer, and the duration of the timer is configured as t1. Then, the effective time limit is T0 + t1.
  • the timer is started; when the timer times out, that is, from the timer start time to the time T0 + t1, the dedicated random access resource is invalidated.
  • the unit used for characterizing time, duration, time period, or time may be a frame, a subframe, a slot, a symbol, or the like, which is not limited in this application.
  • the effective time limit can be set as the deadline. In this way, the deadline of the validity period of the pre-allocated resources is directly specified. Specifically, the deadline of the validity period or the start of the expiration period can be specified.
  • the effective time limit of the second method is clearer. Because the target base station may not be able to confirm when the terminal device can receive the conditional switching command, the time T0 cannot be determined, so the time T0 + t cannot be determined. This method is equivalent to directly indicating the time T0 + t1, so that the base station and the terminal device can clearly confirm this time, for example, it is called time T '.
  • the setting of the cutoff time in the second manner may be in the form of frame number + subframe number, or may be in the form of frame number + subframe number + slot index, which is not limited in this application.
  • the source base station can renegotiate with the target base station to obtain updated time information. For example, the source base station sends a handover request message to the target base station again, and the target base station returns a handover confirmation message. In this way, the target base station updates the cell configuration information in the handover command.
  • the base station may send a conditional switching command to the terminal device again, including the target cell and add modlist, instructing the terminal device to modify one or more of the cell configuration information, and if the configuration information of the validity timer is included , The terminal device updates the configuration of the effective duration and restarts the timer.
  • the time information of T0 + t1 of one or more cells can be updated in the target cell addmod list to extend the validity period of the pre-allocated resources.
  • the source base station can directly send a traditional handover command to the terminal device, and the terminal device will immediately perform the handover after receiving it, and at the same time clear the candidate cell list var target cell list.
  • conditional switching command can add a separate conditional switching instruction to the switching command, on the other hand, it can also be judged by whether the switching command includes a target cell release list or a target cell addmodlist.
  • the two methods can be used independently or independently, which is not limited in the embodiments of the present application.
  • a new random access resource may be allocated to the terminal device, and details are not described herein again.
  • a timer can be set to prevent the terminal device from reporting the measurement report of the cell with poor communication quality;
  • the newly defined P1 event reports a new candidate cell within the operating time after the timer is started, ensuring that the terminal device can select a cell with better communication quality for handover.
  • adjusting the candidate cell list of the terminal device for example, performing addition or deletion of the candidate cell list, or adjusting the validity period of the pre-allocated random access resource, thereby ensuring that the terminal device can select a more suitable target cell, ensuring that the terminal device and Communication quality between base stations.
  • the terminal device After receiving the condition handover command sent by the source base station, the terminal device enters an evaluation state and starts to evaluate whether the handover condition is satisfied. If the terminal device has not yet switched to the target cell, but the communication quality of the source base station is degraded, the source base station with the degraded communication quality may maintain communication with the terminal device through the side link, or the source base station may reserve reporting resources for the terminal device.
  • the present application also provides a method for instructing the terminal device and the source base station to stop communicating, by using an explicit message or an implicit method, indicating When the terminal device and the source base station stop communication, the time point at which data transmission is stopped is clearly avoided to avoid waste of resources.
  • the method for instructing the terminal device and the source base station to stop communication may be applied to the terminal device and the base station, or may be a chip applied to the terminal device and a chip applied to the base station.
  • the terminal device directly sends a stop instruction to the source base station, or relays the instruction through the target base station.
  • the terminal device may directly send a message to the source base station to instruct to stop data transmission. For example, when the terminal device is ready to send a random access preamble to the target base station, the terminal device may send the message indication to the base station.
  • the terminal device does not send an explicit message to the base station.
  • the target base station After the terminal device successfully completes the random access process, the target base station sends a terminal device release message to the source base station. After receiving the message, the source base station stops sending data to the terminal device.
  • the source base station notifies the terminal device to end the communication, for example, the source base station sends an RRC message to the terminal device, where the RRC message is used to instruct to stop data transmission.
  • the terminal device After receiving the RRC message, the terminal device stops communication with the source base station, and then immediately selects a target cell to begin the handover process.
  • a target cell For the selection principle of the target cell, reference may be made to the related description in the method 400.
  • the source base station determines that communication with the terminal device needs to be stopped.
  • the source base station may consider that the terminal device has completed handover, and the source base station may stop sending data to the terminal device at this time. .
  • the terminal device and the source base station are instructed to stop communicating at an instant by explicitly or implicitly, and the time point at which data transmission is stopped can be avoided, thereby avoiding waste of resources.
  • the above describes in combination with FIG. 1 to FIG. 7 a variety of abnormal scenarios, such as a scenario in which the signal strength of the source cell suddenly decreases and the wireless link fails, or when the signal strength of multiple candidate cells decreases, how the terminal device determines the target cell and completes the cell Handover, or the terminal device cannot complete the cell handover for a long time, how the terminal device selects a new and more reasonable target cell, and how to stop data transmission with the source cell, provides corresponding terminal device and base station processing methods, and conditions for handover
  • the method is improved to ensure that a target cell with better communication quality is selected in an abnormal scenario, and cell switching is completed to ensure the accuracy of cell switching and communication between the terminal device and the base station, while avoiding waste of resources.
  • FIG. 8 shows a schematic block diagram of a communication device 800 according to an embodiment of the present application.
  • the device 800 may correspond to the terminal device described in the foregoing method 400, and may also be a chip or component applied to the terminal device. Each module or unit is respectively configured to perform each action or process performed by the terminal device in the foregoing method 400.
  • the communication device 800 may include a communication unit 810 and a processing unit 820.
  • the processing unit 810 obtains a first handover condition and a second handover condition, and the first handover condition and the second handover condition are used by the terminal device to determine a target cell for handover from a plurality of candidate cells.
  • the communication unit 820 when each of the plurality of candidate cells does not satisfy the first handover condition, and when the communication quality of the source cell in which the terminal device is located decreases, the wireless link of the terminal device fails When it is used to determine a handover target cell from the plurality of candidate cells according to the second handover condition. or
  • the communication unit 820 when each candidate cell in the multiple candidate cells does not satisfy the first handover condition, and when the communication quality of the source cell in which the terminal device is located decreases, a wireless link of the terminal device is caused. When a failure occurs, it is used to determine a handover target cell from the plurality of candidate cells according to the second handover condition.
  • the communication unit 810 is used to execute S403 in method 400
  • the processing unit 820 is used to execute S401 and S402 in method 400.
  • the specific process of each unit performing the above corresponding steps has been described in detail in method 400. For the sake of brevity , I won't go into details here.
  • FIG. 9 shows a schematic block diagram of a communication device 900 according to an embodiment of the present application.
  • the device 900 may correspond to the terminal device described in the foregoing method 600, and may also be a chip or component applied to the terminal device. Each module or unit is respectively configured to perform various actions or processing processes performed by the terminal device in the foregoing method 600.
  • the communication device 900 may include a processing unit 910 and a communication unit 920.
  • the processing unit 910 is configured to start a timer.
  • the communication unit 920 is configured to send a measurement report to a network device when the timer expires and the terminal device does not determine a target cell to be switched from the first candidate cell set, and the measurement report is used to determine a second candidate. Cell collection.
  • the communication unit 920 is further configured to receive information of a second candidate cell set from a network device, and determine a target cell to be switched from the second candidate cell set.
  • the processing unit 910 is configured to perform S602, S603, and S606 in method 600
  • the communication unit 920 is configured to perform S601, S604, and S605 in method 600.
  • the specific process of each unit performing the corresponding steps is described in method 600. It has been described in detail, for the sake of brevity, it will not be repeated here.
  • FIG. 10 shows a schematic block diagram of a communication device 1000 according to an embodiment of the present application.
  • the device 1000 may correspond to (for example, be applicable to or be itself) the base station described in the method 400, and each module in the device 1000 The OR units are respectively used to perform various actions or processing processes performed by the base station in the above method 400.
  • the communication device 1000 may include a processing unit 1010 and a communication unit 1020.
  • a communication unit 1010 is configured to send a first handover condition and a second handover condition to a terminal device, where the first handover condition and the second handover condition are used by the terminal device to determine a handover target cell from a plurality of candidate cells. .
  • the communication unit 1010 is further configured to receive a handover completion message sent by the target base station, where the handover completion message is used to indicate that the terminal device has handed over to the target cell.
  • a processing unit 1020 configured to: when each candidate cell of the plurality of candidate cells does not satisfy the first handover condition, and when the communication quality of the source base station is degraded and the wireless link of the terminal device fails, the target The cell is determined by the terminal device from the plurality of candidate cells according to the second handover condition; or when at least two candidate cells in the plurality of candidate cells meet the first handover condition, all cells The target cell is determined by the terminal device from the at least two candidate cells according to the second handover condition, and the target base station provides the target cell to the terminal device.
  • the communication unit 1010 is configured to execute S403 in the method 400.
  • the specific process of each unit performing the foregoing corresponding steps has been described in detail in the method 400. For brevity, details are not described herein.
  • FIG. 11 shows a schematic block diagram of a communication device 1100 according to an embodiment of the present application.
  • the device 1100 may correspond to (for example, be applicable to or be itself) the base station described in the above method 600, and each module in the device 1100 The OR units are respectively used to perform various actions or processing processes performed by the base station in the above method 600.
  • the communication device 1100 may include a processing unit 1111 and a communication unit 1120.
  • the communication unit 1110 is configured to send a condition switching command.
  • the communication unit 1110 is further configured to receive a measurement report from the terminal device when the terminal device does not determine a target cell to be switched from the first candidate cell set outside the first duration.
  • the processing unit 1120 is configured to determine a second candidate cell set according to the measurement report, and the first duration is a running duration of the terminal device timer.
  • the communication unit 1110 is further configured to send information about the second candidate cell set to the terminal device.
  • the communication unit 1110 is configured to perform S601, S604, and S605 in method 600
  • the processing unit 1120 is configured to perform S602, S603, and S606 in method 600.
  • the specific process of each unit performing the corresponding steps is described in method 600. It has been described in detail, for the sake of brevity, it will not be repeated here.
  • FIG. 12 is a schematic structural diagram of a terminal device 1200 according to an embodiment of the present application.
  • the terminal device 1200 includes a processor 1210 and a transceiver 1220.
  • the terminal device 1200 further includes a memory 1230.
  • the processor 1210, the transceiver 1220, and the memory 1230 communicate with each other through an internal connection path to transfer control and / or data signals.
  • the memory 1230 is used to store a computer program, and the processor 1210 is used to call from the memory 1230.
  • the computer program is run to control the transceiver 1220 to send and receive signals.
  • the processor 1210 and the memory 1230 may be combined into a processing device, and the processor 1210 is configured to execute program code stored in the memory 1230 to implement the functions of the terminal device in the foregoing method embodiment.
  • the memory 1230 may also be integrated in the processor 1210 or independent of the processor 1210.
  • the transceiver 1220 may be implemented by means of a transceiver circuit.
  • the terminal device may further include an antenna 1240 for sending uplink data or uplink control signaling output by the transceiver 1220 through a wireless signal, or sending downlink data or downlink control signaling to the transceiver 1220 for further processing.
  • the device 1200 may correspond to the terminal device in the method 400 or the method 600 according to the embodiment of the present application, and the device 1200 may also be a chip or a component applied to the terminal device.
  • each module in the apparatus 1200 implements the corresponding process in the method 400 in FIG. 4, or each module in the apparatus 1200 implements the corresponding process in the method 600 in FIG. 6.
  • the memory 1230 is configured to store program code, so that the processor 1210 controls the processor 1210 to execute S401 and S402 in the method 400 when the program code is executed, and the transceiver 1220 is used to execute the method 400 in the method 400.
  • S403, or the memory 1230 is used to store program code, so that when the processor 1210 executes the program code, the processor 1210 is controlled to execute S602, S603, and S606 in the method 600, and the transceiver 1220 is used to execute the method S601, S604, and S605 in 600.
  • the specific process of each unit performing the above corresponding steps has been described in detail in the method 400 and the method 600. For the sake of brevity, details are not described herein.
  • FIG. 13 is a schematic structural diagram of a network device 1300 according to an embodiment of the present application.
  • the network device 1300 (for example, a base station) includes a processor 1310 and a transceiver 1313.
  • the network device 1300 further includes a memory 1330.
  • the processor 1310, the transceiver 1313, and the memory 1330 communicate with each other through an internal connection path to transfer control and / or data signals.
  • the memory 1330 is used to store a computer program, and the processor 1310 is used to call from the memory 1330.
  • the computer program is run to control the transceiver 1313 to send and receive signals.
  • the processor 1310 and the memory 1330 may be combined into a processing device.
  • the processor 1310 is configured to execute the program code stored in the memory 1330 to implement the functions of the base station in the foregoing method embodiment.
  • the memory 1330 may also be integrated in the processor 1310, or may be independent of the processor 1310.
  • the transceiver 1313 can be implemented by means of a transceiver circuit.
  • the above network device may further include an antenna 1340 for sending downlink data or downlink control signaling output by the transceiver 1313 through a wireless signal, or sending uplink data or uplink control signaling to the transceiver 813 for further processing after receiving.
  • the device 1300 may correspond to the base station in the method 400 or the method 600 according to the embodiment of the present application, and the device 1300 may also be a chip or a component applied to a base station.
  • each module in the device 1300 implements a corresponding process in the method 400 in FIG. 4 or the method 600 in FIG. 6.
  • the memory 1330 is used to store program code, so that the processor 1310 controls the transceiver 1320 to execute S403 in method 400 when the program code is executed, or the memory 1330 is used to store the program code so that processing
  • the processor 1310 controls the processor 1310 to execute S602, S603, and S606 in the method 600 when the program code is executed
  • the transceiver 1320 is used to execute S601, S604, and S605 in the method 600.
  • the specific process for each unit to execute the above corresponding steps has been described in detail in method 400 and method 600. For brevity, details are not described herein again.
  • the disclosed systems, devices, and methods may be implemented in other ways.
  • the device embodiments described above are only schematic.
  • the division of the unit is only a logical function division.
  • multiple units or components may be combined or Can be integrated into another system, or some features can be ignored or not implemented.
  • the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, which may be electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objective of the solution of this embodiment.
  • each functional unit in each embodiment of the present application may be integrated into one processing unit, or each of the units may exist separately physically, or two or more units may be integrated into one unit.
  • the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium.
  • the technical solution of this application is essentially a part that contributes to the existing technology or a part of the technical solution can be embodied in the form of a software product.
  • the computer software product is stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in the embodiments of the present application.
  • the aforementioned storage media include: U disks, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks or compact discs and other media that can store program codes .

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Abstract

La présente invention concerne un procédé et un dispositif de commutation de cellule. Dans le procédé, un temporisateur est configuré pour un dispositif terminal, de telle sorte que, lorsque le dispositif terminal n'a pas terminé un transfert pendant une longue période, un rapport de mesure n'est pas envoyé dans la durée définie du temporisateur pour empêcher le dispositif terminal de rapporter un rapport de mesure d'une cellule ayant une faible qualité de communication ; un événement de mesure est redéfini et une nouvelle cellule candidate est rapportée pendant une durée de fonctionnement après activation du temporisateur, de manière à garantir que le dispositif terminal peut sélectionner une cellule ayant une meilleure qualité de communication pour effectuer un transfert ; et après qu'un dispositif de réseau détermine un ensemble de cellules candidates au moyen du rapport de mesure, le dispositif terminal détermine à partir de l'ensemble de cellules candidates une cellule cible pour subir un transfert intercellulaire, ce qui garantit que le dispositif terminal peut sélectionner une cellule cible plus appropriée et assurer en outre une qualité de communication entre un dispositif terminal et une station de base.
PCT/CN2018/107939 2018-09-27 2018-09-27 Procédé et dispositif de commutation de cellule WO2020061899A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220078684A1 (en) * 2019-05-13 2022-03-10 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. User equipment supporting conditional handovers to cells of a cellular network and a cellular network supporting conditional handovers

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CN101827384A (zh) * 2009-03-06 2010-09-08 大唐移动通信设备有限公司 一种小区切换的方法和基站
CN102857964A (zh) * 2011-06-28 2013-01-02 中兴通讯股份有限公司 一种终端切换的方法及装置
WO2013113200A1 (fr) * 2012-01-31 2013-08-08 中兴通讯股份有限公司 Procédé et dispositif pour traiter une liste de cellules et terminal mobile

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Publication number Priority date Publication date Assignee Title
CN101827384A (zh) * 2009-03-06 2010-09-08 大唐移动通信设备有限公司 一种小区切换的方法和基站
CN102857964A (zh) * 2011-06-28 2013-01-02 中兴通讯股份有限公司 一种终端切换的方法及装置
WO2013113200A1 (fr) * 2012-01-31 2013-08-08 中兴通讯股份有限公司 Procédé et dispositif pour traiter une liste de cellules et terminal mobile

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Publication number Priority date Publication date Assignee Title
US20220078684A1 (en) * 2019-05-13 2022-03-10 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. User equipment supporting conditional handovers to cells of a cellular network and a cellular network supporting conditional handovers

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