Cell handover methods, terminal devices and network devices

Abstract

Provided in the present application are cell handover methods, terminal devices and network devices. A method comprises: during L1 / L2 handover, a terminal device receives a first TA, the first TA being a TA of the terminal device relative to a target cell, and the first TA being effective during an operation period of a first TAT of the terminal device. The present application determines an effective time of a TA of a target cell on the basis of a TAT of a terminal device, thereby improving the reliability of communication.

Description

Cell switching method, terminal device and network device Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular to a cell switching method, terminal equipment, and network equipment. Background Art

[0002] In a wireless communication system, a terminal device may need to obtain a time advance (TA) relative to a target cell in advance during a cell handover process. However, how to determine the validity of the TA obtained in advance by the terminal device is still unclear.

[0003] Summary of the Invention

[0004] The embodiments of the present application provide a cell handover method, a terminal device, and a network device, which are described below from the following aspects.

[0005] In a first aspect, a cell switching method is provided, including: during a layer 1 (L1) / layer 2 (L2) switching process, a terminal device receives a first TA, where the first TA is the TA of the terminal device relative to a target cell, and the first TA is valid during the operation period of a first time alignment timer (TAT) of the terminal device.

[0006] In the second aspect, a cell switching method is provided, including: during the L1 / L2 switching process, the source cell receives a first TA, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0007] In a third aspect, a cell switching method is provided, including: during the L1 / L2 switching process, the target cell sends a first TA, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0008] In a fourth aspect, a terminal device is provided, comprising: a receiving module for receiving a first TA during the L1 / L2 switching process, wherein the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0009] In the fifth aspect, a network device is provided, which is a network device corresponding to a source cell, and the device includes: a transceiver module for receiving a first TA during the L1 / L2 switching process, wherein the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0010] In the sixth aspect, a network device is provided, which is a network device corresponding to a target cell, and the device includes: a transceiver module for sending a first TA during the L1 / L2 switching process, wherein the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0011] In the seventh aspect, a terminal device is provided, comprising a transceiver, a memory and a processor, wherein the memory is used to store programs, and the processor is used to call the programs in the memory and control the transceiver to receive or send signals so that the terminal device executes the method as described in any one of the first aspects.

[0012] In the eighth aspect, a network device is provided, comprising a transceiver, a memory and a processor, wherein the memory is used to store programs, and the processor is used to call the programs in the memory and control the transceiver to receive or send signals so that the network device executes the method as described in any one of the second aspects.

[0013] In the ninth aspect, a network device is provided, comprising a transceiver, a memory and a processor, wherein the memory is used to store programs, and the processor is used to call the programs in the memory and control the transceiver to receive or send signals so that the network device executes the method as described in any one of the third aspects.

[0014] In a tenth aspect, a device is provided, comprising a processor for calling a program from a memory so that the device executes a method as described in any one of the first aspect, the second aspect, or the third aspect.

[0015] In the eleventh aspect, a chip is provided, comprising a processor for calling a program from a memory so that a device equipped with the chip executes a method as described in any one of the first aspect, the second aspect or the third aspect.

[0016] In the twelfth aspect, a computer-readable storage medium is provided, on which a program is stored, wherein the program enables a computer to execute the method as described in any one of the first aspect, the second aspect or the third aspect.

[0017] In a thirteenth aspect, a computer program product is provided, comprising a program, wherein the program enables a computer to execute the method as described in any one of the first aspect, the second aspect or the third aspect.

[0018] In a fourteenth aspect, a computer program is provided, which enables a computer to execute the method as described in any one of the first aspect, the second aspect or the third aspect.

[0019] In the present application, the effective time of the TA of the target cell is determined based on the TAT of the terminal device, thereby improving the reliability of communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a diagram illustrating an example of a system architecture of a wireless communication system to which an embodiment of the present application may be applied.

[0021] FIG2 is a schematic diagram of the system structure of the CU and DU separation architecture.

[0022] FIG3 is a schematic flow chart of a bottom layer fast switching method.

[0023] FIG4 is a schematic flowchart of a cell switching method provided in an embodiment of the present application.

[0024] FIG5 is a diagram showing an example of a classification of a random access process in an embodiment of the present application.

[0025] FIG6 is an example diagram of a cell switching method provided in an embodiment of the present application.

[0026] FIG7 is a schematic diagram of the structure of the terminal device provided in an embodiment of the present application.

[0027] FIG8 is a schematic diagram of the structure of a network device provided by an embodiment of the present application.

[0028] FIG9 is a schematic structural diagram of a network device provided in another embodiment of the present application.

[0029] FIG10 is a schematic diagram of the structure of the device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0031] Communication system architecture

[0032] FIG1 is a diagram illustrating an exemplary system architecture of a wireless communication system 100 to which embodiments of the present application may be applied. The wireless communication system 100 may include a network device 110 and a terminal device 120. The network device 110 may be a device that communicates with the terminal device 120. The network device 110 may provide communication coverage for a specific geographic area and may communicate with the terminal device 120 within the coverage area.

[0033] FIG1 exemplarily shows a network device and a terminal device. Optionally, the wireless communication system 100 may include one or more network devices 110 and / or one or more terminal devices 120. For a network device 110, the one or more terminal devices 120 may all be located within the network coverage of the network device 110, or all be located outside the network coverage of the network device 110, or some may be located within the coverage of the network device 110 and others outside the network coverage of the network device 110. This is not limited in the embodiments of the present application.

[0034] Optionally, the wireless communication system 100 may further include other network entities such as a network controller and a mobility management entity, which is not limited in the embodiment of the present application.

[0035] It should be understood that the technical solutions of the embodiments of the present application can be applied to various communication systems, such as: fifth generation (5G) system or new radio (NR) system, long term evolution (LTE) system, LTE frequency division duplex (FDD) system, LTE time division duplex (TDD) system, etc. The technical solutions provided in this application can also be applied to future communication systems, such as the sixth generation mobile communication system, satellite communication system, etc.

[0036] The terminal device in the embodiments of the present application may also be referred to as user equipment (UE), access terminal, user unit, user station, mobile station, mobile station (MS), mobile terminal (MT), remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent or user device. The terminal device in the embodiments of the present application may refer to a device that provides voice and / or data connectivity to a user and can be used to connect people, objects and machines, such as a handheld device with wireless connection function, a vehicle-mounted device, etc. The terminal device in the embodiments of the present application can be a mobile phone, a tablet computer, a laptop computer, a PDA, a mobile internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical surgery, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, etc. Optionally, the UE can be used to act as a base station. For example, the UE can act as a scheduling entity that provides sidelink signals between UEs in vehicle-to-everything (V2X) or device-to-device (D2D). For example, a cellular phone and a car communicate with each other using sidelink signals. The cellular phone and smart home devices communicate without relaying the communication signal through the base station.

[0037] The network device in the embodiments of the present application may be a device for communicating with a terminal device, and may also be referred to as an access network device or a radio access network device. For example, the network device may be a base station. The network device in the embodiments of the present application may refer to a radio access network (RAN) node (or device) that connects a terminal device to a wireless network. A base station may broadly cover various names as follows, or replace the following names, such as: NodeB, evolved NodeB (eNB), next generation NodeB (gNB), relay station, access point, transmitting and receiving point (TRP), transmitting point (TP), master station MeNB, secondary station SeNB, multi-standard radio (MSR) node, home base station, network controller, access node, wireless node, access point (AP), transmission node, transceiver node, baseband unit (BBU), remote radio unit (RRU), active antenna unit (AAU), remote radio head (RRH), central unit (CU), distributed unit (DU), positioning node, etc. A base station may be a macro base station, a micro base station, a relay node, a donor node, or the like, or a combination thereof. A base station may also refer to a communication module, modem, or chip used to be set in the aforementioned device or apparatus. A base station may also be a mobile switching center and a device that performs base station functions in device-to-device D2D, V2X, or machine-to-machine (M2M) communications, a network-side device in a 6G network, or a device that performs base station functions in future communication systems. A base station may support networks with the same or different access technologies. The embodiments of this application do not limit the specific technology and specific device form used by network devices.

[0038] Base stations can be fixed or mobile. For example, a helicopter or drone can be configured to act as a mobile base station, and one or more cells can move based on the location of the mobile base station. In other examples, a helicopter or drone can be configured to act as a device that communicates with another base station.

[0039] In some deployments, the network device in the embodiments of the present application may refer to a CU or a DU, or the network device may include a CU and a DU. The gNB may also include an AAU.

[0040] The network equipment and terminal devices can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; they can also be deployed on water; they can also be deployed in the air on aircraft, balloons, and satellites. The embodiments of this application do not limit the scenarios in which the network equipment and terminal devices are located.

[0041] It should be understood that all or part of the functions of the communication device in this application can also be implemented through software functions running on hardware, or through virtualization functions instantiated on a platform (such as a cloud platform).

[0042] Control unit (CU) and data unit (DU) separation architecture

[0043] The 5G wireless communication network system implements the separation of control units (CUs) and user units (DUs), with one CU managing hundreds or even thousands of DUs. From the perspective of the communication protocol stack, the control plane entities reside in the CU, while the user plane entities reside in both the CU and the DUs. As shown in Figure 2, for the user plane entities, the CU includes the service data adaptation protocol (SDAP) layer and the packet data convergence protocol (PDCP) layer, while the DU includes the radio link control (RLC) layer, the medium access control (MAC) layer, and the physical (PHY) layer.

[0044] In a separate architecture with CU and DU, terminal devices can switch cells in three ways. The first type is handover without DU replacement: neither the DU nor the CU changes before or after the cell switch. The second type is handover without CU replacement: neither the DU nor the CU changes before or after the cell switch. The third type is handover with CU replacement: both the DU and the CU change before or after the cell switch.

[0045] L1 / L2 switching

[0046] In order to reduce the delay of the terminal device switching cells, the relevant technology introduces an L1 / L2 switching method, which can also be called a bottom-layer fast switching method. The bottom-layer fast switching method involves the terminal device obtaining (also known as pre-acquisition) the TA of the target cell in advance. The process of this method can be shown in Figure 3, including steps S310-S380. The target cells that the terminal device can select include target cell 1, target cell 2 and target cell 3. The switching from the source cell to the target cell 1 is a switching without changing the DU, the switching from the source cell to the target cell 2 is a switching with changing the DU, and the switching from the source cell to the target cell 3 is a switching with changing the CU.

[0047] In step S310, the source cell sends a handover preparation message to each target cell.

[0048] In step S320, the source cell receives the handover preparation completion message sent by each target cell.

[0049] In step S330, the cell sends a quasi-target cell list to the terminal device through a handover configuration message of the radio resource control (RRC) layer. The quasi-target cell list includes configuration information of all candidate cells (including whether to perform an L2 reset on each target cell).

[0050] In step S340, the terminal device initiates a random access preamble to each cell based on the configuration information to perform random access, acquire the TA in advance, and measure each cell. The TA can be notified to the terminal device by the target cell, or the target cell may not notify the terminal device of the TA, but may notify the source cell of the TA, which will then store the TA.

[0051] In step S350, the terminal device reports the measurement results of each candidate target cell to the source cell, and the source cell determines the target cell for handover.

[0052] In step S360, after the source cell determines the target cell, it notifies the terminal device via L1 / L2 signaling. For example, the target cell determined by the source cell may be target cell 1, target cell 2, or target cell 3.

[0053] In step S370, the terminal device sends uplink data to the target cell. At this point, if the terminal device has pre-acquired the target cell's TA and the target base station has allocated configured grant (CG) resources to the terminal device, the terminal device directly sends the uplink data. Otherwise, the terminal device obtains uplink resources and TA through a random access process and sends the uplink data.

[0054] In step S380, the terminal device receives a confirmation message from the target cell, and the handover process ends.

[0055] As described above, during the L1 / L2 handover process, to reduce handover latency, the terminal device will pre-acquire the target cell's TA. However, there are currently no clear regulations on how long this TA is valid (or how the terminal device, source cell, or target cell determines whether the pre-acquired TA is valid).

[0056] In response to the above problems, the technical solutions provided by the embodiments of the present application are described in detail below.

[0057] FIG4 is a flow chart of a cell handover method according to an embodiment of the present application. The method of FIG4 may be executed by a terminal device. The terminal device may be any of the terminal devices mentioned in the above embodiments, such as the terminal device 120 in FIG1 .

[0058] 4 , as shown in steps S410 to S420 , during the L1 / L2 handover process, the target cell sends a first TA to the source cell. After receiving the first TA, the source cell may send the first TA to the terminal device.

[0059] The first TA is the TA of the terminal device relative to the target cell. In other words, the first TA corresponds to the terminal device and the target cell.

[0060] It should be understood that steps S410 to S420 may be performed in the early TA acquisition phase of the L1 / L2 switching process.

[0061] In some implementations, the target cell may also directly send the first TA to the terminal device (not shown in the figure).

[0062] Before step S410, the terminal device may first send a random access message (for carrying a preamble) to the target cell to obtain a first TA.

[0063] For example, the terminal device may first send a random access message to the target cell. After receiving the random access message sent by the terminal device, the target cell may first transmit the first TA to the source cell, and then the source cell may transmit the first TA to the terminal device. For example, the source cell may send L1 / L2 handover indication information to the terminal device, and the L1 / L2 handover indication information may carry the first TA.

[0064] For another example, the target cell may allocate a cell-radio network temporary identifier (C-RNTI) to the terminal device in advance, and then send the first TA to the terminal device based on the C-RNTI. For example, the terminal device may first receive the C-RNTI allocated by the target cell to the terminal device (which may be obtained through the handover configuration message sent by the source cell, or through the PDCCH order sent by the source cell). Then, the terminal device may send a random access message to the target cell. Then, the terminal device may monitor the physical downlink control channel (PDCCH) of the target cell based on the C-RNTI, thereby receiving the first TA.

[0065] In some implementations, the first TA is valid during the operation period of the first TAT of the terminal device. The first TAT can be the TAT configured by the source cell for the terminal device, or it can be the TAT specified by the protocol. The timing duration (or value) of the first TAT can be determined by the moving speed of the terminal device. For example, the faster the terminal device moves, the shorter the timing duration of the first TAT, which means that the value of the first TA needs to be updated frequently. For another example, if the terminal device moves slowly, the longer the timing duration of the first TAT, the frequency of updating the value of the first TA can be relatively low. If the moving speed of the terminal device does not change much in the short term, the timing duration of the first TAT can remain unchanged. The embodiment of the present application determines the effective time of the TA of the target cell based on the TAT of the terminal device, thereby improving the reliability of communication.

[0066] The source cell may send the first TAT to the target cell so that the target cell determines the length of the validity period of the first TAT according to the first TAT. The embodiment of the present application does not specifically limit the timing of sending the first TAT.

[0067] In some implementations, the source cell may send the first TAT to the target cell in a handover prepare message.

[0068] In some implementations, the source cell may also send the first TAT to the target cell after sending the handover preparation message to the target cell. For example, the source cell may wait until the target cell notifies the source cell of the first TAT before sending the first TAT to the target cell. In this case, the target cell does not yet know which terminal device the first TAT is intended for and can only simply record the mapping between the first TAT and its allocated uplink resources.

[0069] The embodiment of the present application does not specifically limit the timing for the source cell, the target cell, and the terminal device to initiate the first TAT.

[0070] In some implementations, the source cell may start the first TAT upon receiving the first TA sent by the target cell. For example, the source cell may send the first TAT to the target cell via a handover preparation message. In this case, the source cell and the target cell may determine the start time of the first TAT based on the transmission time of the first TA. For example, the target cell may start the first TAT after sending the first TA to the source cell; the source cell may start the first TAT after receiving the first TA.

[0071] In some implementations, the source cell may also activate the first TAT after receiving the first TA from the target cell and returning the first TAT to the target cell. For example, the source cell does not send the first TAT to the target cell via a handover preparation message, but instead waits to send the first TAT to the target cell after receiving the first TA. In this case, the source cell and the target cell may determine the activation time of the first TAT based on the transmission time of the first TAT. For example, the source cell may activate the first TAT after sending the first TAT to the target cell; the target cell may activate the first TAT after receiving the first TAT.

[0072] In some implementations, the terminal device may initiate the first TAT after receiving the first TA sent by the target cell. For example, as described above, the target cell directly sends the first TA to the terminal device, and the terminal device may initiate the first TAT after receiving the first TA; the target cell may initiate the first TAT after sending the first TA.

[0073] In the case where a terminal device sends a random access message to multiple target cells, the source cell and / or the terminal device may start multiple first TATs corresponding to the first TA of each target cell after receiving the first TAs of the multiple target cells, and the values ​​of the multiple first TATs may be the same.

[0074] After the first TAT is started, its running time can be determined based on the timer duration of the first TAT. For example, the running time of the first TAT can be the timer duration of the first TAT. Then, after the first TAT is started, the first TA is valid within the timer duration of the first TAT.

[0075] For the terminal device, the running time of the first TAT may also be determined based on the remaining time of the first TAT indicated by the source cell. The running time of the first TAT may be the remaining time of the first TAT indicated by the source cell. The remaining time of the first TAT may be the remaining time of the first TAT started in the source cell.

[0076] For example, in the case where the first TA is transmitted to the terminal device via the source cell, the source cell may notify the terminal device of the first TA and the remaining time of the first TAT in the L1 / L2 switching indication. After the terminal device receives the remaining time of the first TAT indicated by the source cell, it may start a timer based on the remaining time of the first TAT, and the first TA is valid during the running time of the timer. For example, the value of the first TAT is 1000, and the source cell starts the first TAT after receiving the TA value sent by the target cell. When the underlying fast switching is triggered, the TAT has been running for 300ms, and the source cell indicates 700ms to the terminal device, indicating that "within 700ms, the pre-acquired TA is valid." After receiving the indication, the terminal device may start a timer with a timing duration of 1000ms and an initial value of 300ms, or set the timer duration to 700ms and an initial value of 0, and the pre-acquired TA is valid during the time of the timer.

[0077] In some implementations, if the terminal device resends a random access message to the target cell before the first TAT times out, the first TAT is restarted. For example, the target cell reissues the first TAT in response to the random access message resent by the terminal device and restarts the first TAT. The terminal device or source cell restarts the first TAT after re-receiving the first TAT. Alternatively, the terminal device restarts a timer it started when it re-receives the remaining time of the first TAT.

[0078] In some implementations, the method of Figure 4 may further include: the target cell sends first configuration information to the source cell (such as through a handover preparation completion message). Accordingly, the source cell may send part or all of the information in the first configuration information to the terminal device (such as through a handover configuration message). In some implementations, the first configuration information may be used to indicate one or more of the following information: the C-RNTI allocated by the target cell to the terminal device; the CG resources allocated by the target cell to the terminal device; the PDCCH monitoring space allocated by the target cell to the terminal device; the dedicated physical random access channel (PRACH) resources allocated by the target cell to the terminal device; and a scheduling request (SR) configuration.

[0079] In some implementations, the target cell may send the first configuration information to the source cell via a handover preparation complete message. For example, after receiving the handover preparation message from the source cell, the target cell may perform admission control on the terminal device, and carry the C-RNTI allocated by the target cell to the terminal device; the CG resources allocated by the target cell to the terminal device; the PDCCH monitoring space allocated by the target cell to the terminal device; and the SR configuration in the handover preparation complete message. For another example, after receiving the handover preparation message from the source cell, the target cell may only perform admission control on the terminal device, and not carry the C-RNTI allocated by the target cell to the terminal device; the CG resources allocated by the target cell to the terminal device; the PDCCH monitoring space allocated by the target cell to the terminal device; and the SR configuration in the handover preparation complete message. The above information can be notified to the source cell by the target cell after the terminal device successfully obtains the TA in advance. For example, after sending the first TA to the terminal device, the target cell may add a step in which the target cell sends a notification message to the source cell. The notification message may be called a terminal device information indication message, and the above information is transmitted through the terminal device information indication message. Of course, part of the above information can also be transmitted in the switching preparation completion message, and part can be transmitted in the terminal device information indication message. The embodiment of the present application does not make specific limitations on this.

[0080] In some implementations, if the first configuration information includes a dedicated PRACH resource allocated by the target cell to the terminal device, the dedicated PRACH resource may be carried in a handover preparation complete message.

[0081] In some implementations, the source cell may send the first configuration information to the terminal device via a handover configuration message, for example, after receiving a handover preparation message sent by the target cell.

[0082] It should be understood that the handover configuration message may carry all the information in the first configuration information, or may carry only part of the information in the first configuration information. In some implementations, the information content carried by the handover configuration message may be related to the information content provided by the target cell to the source cell through the handover preparation complete message. For example, if the target cell includes the C-RNTI allocated by itself to the terminal device in the handover preparation complete message, the source cell may notify the terminal device of the C-RNTI in the handover configuration message. For another example, if the target cell includes information about the CG resources allocated by itself to the terminal device in the handover preparation complete message, the source cell may indicate the CG resources to the terminal device in the handover configuration message. For another example, if the target cell includes information about the PDCCH monitoring space allocated by itself to the terminal device in the handover preparation complete message, the source cell may indicate the PDCCH monitoring space (or control resource set (CORESET)) to the terminal device in the handover configuration message. For another example, if the target cell includes the SR configuration allocated by itself to the terminal device in the handover preparation complete message, the source cell may indicate the SR configuration to the terminal device in the handover configuration message. For another example, if the target cell includes information about the dedicated PRACH resources allocated to the terminal device in the handover preparation complete message, the source cell can indicate the dedicated PRACH resources to the terminal device in the handover configuration message. It is worth noting that even if the target cell includes the above information of the terminal device in the handover preparation complete message, the source cell can provide all of the above information to the terminal device, or only provide part of the above information to the terminal device. If the source cell only provides part of the above information to the terminal device in the handover configuration message, the other information can be provided to the terminal device when the source cell sends an L1 / L2 handover indication to the terminal device.

[0083] In some implementations, if the first configuration information only indicates CG resources, after the terminal device switches to the target cell, the first uplink data (or the first transmission block (TB)) in the target cell can be transmitted through the CG resources.

[0084] In some implementations, if the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell can be transmitted using dynamic grant (DG), where the DG is determined based on the PDCCH monitoring space. For example, after the terminal device switches to the target cell, it can monitor the PDCCH in the target cell to obtain the DG, and then send the first uplink data to the target cell using the uplink resources allocated by the DG.

[0085] In some implementations, if the first configuration information indicates CG resources and PDCCH monitoring space (used to determine DG), the terminal device can choose whether to use CG resources or DG to transmit the first uplink data.

[0086] In some implementations, if the first configuration information indicates CG resources and PDCCH monitoring space (used to determine DG), the terminal device may use the uplink resource with the earlier transmission time among the CG resources and the DG to transmit the first uplink data. In other words, if the transmission timing of the CG resource arrives first, the first uplink data is transmitted using the CG resource; if the transmission timing of the DG arrives first, the first uplink data is transmitted using the DG.

[0087] In some implementations, if the target cell allocates an SR for the terminal device, the terminal device can request uplink resources from the target cell through the SR, then monitor the PDCCH of the target cell to obtain the uplink resources allocated by the target cell. The uplink resources can then be used to transmit the first uplink data.

[0088] The first TA mentioned above can be determined by a random access process initiated by the terminal device (the random access process can occur in the early acquisition phase of the TA). There are many ways to implement the random access process. The following is a brief example of how to implement the random access process of the terminal device.

[0089] Random access process of terminal equipment

[0090] In order to obtain the first TA, the random access process initiated by the terminal device can be a contention-based random access process or a non-contention-based random access process. The detailed classification of the random access process initiated by the terminal device can be shown in Figure 5.

[0091] If it is a contention-based random access procedure, it can be triggered by the source cell, the target cell, or the terminal device itself. The contention-based random access procedure triggered by the target cell may include: the target cell triggering based on the MAC control element (CE), or the target cell triggering based on the PDCCH command. The contention-based random access procedure triggered by the source cell may include: the source cell triggering based on the handover configuration message, the source cell triggering based on the MAC CE, or the source cell triggering based on the PDCCH command.

[0092] If triggered by the target cell, the terminal device needs to listen to the notification of the target cell, which will affect the data transmission of the terminal device in the source cell. If triggered by the source cell, or selected by the terminal device itself, it will not affect the data transmission of the terminal device in the source cell. It is worth noting that this also includes a triggering mode: that is, the target cell wants the terminal device to initiate random access, the target cell notifies the source cell, and then the source cell notifies the terminal device "please initiate contention-based random access". This situation is also classified as random access triggered by the source cell and does not affect the data transmission of the terminal device in the source cell.

[0093] If the random access procedure is non-contention-based, it can be triggered by the source cell or the target cell. If it is triggered by the target cell, the source cell must notify the terminal device of the "C-RNTI allocated by the target cell to the terminal device", and the terminal device must also monitor the PDCCH of the target cell, which will adversely affect the terminal device's data transmission in the source cell.

[0094] In some implementations, if a non-contention-based random access process is triggered by a source cell, the non-contention-based random access process may be initiated based on a first dedicated PRACH resource. The first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell. The first PRACH resource set may be a resource set dedicated to random access allocated by the target cell to the source cell. The first PRACH resource set may be allocated when a connection is established between base stations, or may be allocated after a connection is established between base stations. The source cell may allocate a portion of resources from the first PRACH resource set specifically for the terminal device to use for random access to the target cell, and ensure that this portion of resources will not be allocated to other terminal devices, thereby avoiding contention between multiple terminal devices.

[0095] For example, the target cell can allocate a random access resource pool to the source cell. If a terminal device in the source cell needs to switch to the target cell, it can use one of these random access resources to initiate a random access procedure to the target cell. Furthermore, as long as the source cell ensures that the same resource in the resource pool is not allocated to multiple terminal devices, contention is avoided.

[0096] Furthermore, the source cell can indicate the first dedicated PRACH resource to the terminal device via a PDCCH command. After receiving the PDCCH command, the terminal device initiates random access to the target cell based on the first dedicated PRACH resource. The PDCCH command needs to indicate the "cell identifier of the target cell" to the terminal device. Since the PDCCH command is scrambled by the C-RNTI allocated by the source cell, there is no need for the target cell to allocate a C-RNTI to the terminal device.

[0097] In some implementations, if the non-contention-based random access procedure is triggered by the source cell, the non-contention-based random access procedure may also be initiated based on a second dedicated PRACH resource, where the second dedicated PRACH resource is allocated to the terminal device by the target cell. For example, if the target cell allocates a dedicated PRACH resource to the terminal device in the first configuration information, and the source cell notifies the terminal device of the information about the dedicated PRACH resource, the terminal device may directly initiate a random access procedure to the target cell using the dedicated PRACH resource.

[0098] The random access process triggered by the source cell may be triggered based on a first message. The source cell may send a first message to the terminal device to trigger the terminal device to initiate a random access process. The first message may be a PDCCH command, a handover configuration message, or a MAC CE.

[0099] In some implementations, if the target cell does not provide the first PRACH resource set for the source cell and the target cell does not allocate a second dedicated PRACH resource for the terminal device, the source cell may also notify the terminal device through a first message to monitor the PDCCH of the target cell to trigger random access. After monitoring the PDCCH command from the target cell, the terminal device may initiate non-contention random access to the target cell according to the PDCHH command of the target cell. To achieve this random access, the terminal device should know the C-RNTI allocated to the terminal device by the target cell.

[0100] When the source cell triggers random access, it can simultaneously trigger the same terminal device to initiate random access to multiple quasi-target cells to obtain the first TA in advance. Under normal circumstances, the source cell can only trigger the next random access after the previous triggered random access ends. If the terminal device does not need to listen to the random access response (RAR) after sending the preamble, and the target cell sends the measured TA value to the source cell, the source cell does not need to wait until the random access ends before triggering the next random access. The source cell can trigger the next random access immediately after the terminal device sends the preamble, or it can trigger the next random access before the terminal device sends the preamble, and it can also trigger the terminal device to send preamble to multiple quasi-target cells in the same PDCCH order.

[0101] After receiving the preamble of the terminal device, the target cell may decide to notify the first TA to the terminal device and / or the target cell according to whether the target cell knows the purpose of random access of the terminal device.

[0102] In some implementations, if the target cell knows that the purpose of the terminal device initiating random access is to pre-acquire the first TA, the target cell may notify the source cell of the first TA value, or may notify the terminal device of the first TA value. For example, if the random access process is initiated based on the second dedicated PRACH resource, and the target cell receives the preamble of the terminal device from the second dedicated PRACH resource, the target cell believes that the purpose of the terminal device initiating random access is to pre-acquire the first TA. In this case, the target cell may notify the source cell of the first TA value, or may notify the terminal device of the first TA value.

[0103] In other implementations, if the target cell does not know the purpose of the terminal device initiating random access, it can only notify the terminal device of the first TA, and cannot notify the source cell of the first TA value.

[0104] Therefore, for contention-based random access, the target cell can only send the first TA to the terminal device, and cannot send the first TA to the source cell; for non-contention-based random access, the target cell can send the first TA to the terminal device, and can also send the first TA to the source cell.

[0105] After the target cell sends the first TA to the terminal device and / or the target cell, if the target cell is clear about the identity of the terminal device, the target cell can start the TAT corresponding to the terminal device. For example, the random access process is initiated based on the second dedicated PRACH resource, that is, the PRACH resource allocated by the target cell to the terminal device, then the target cell is clear about the identity of the terminal device, and the target cell can start the TAT corresponding to the terminal device after sending the first TA. If the target cell is not clear about the identity of the terminal device, the source cell needs to notify the target cell of the TAT used by the terminal device corresponding to the first TA. For example, the random access process is initiated based on the first dedicated PRACH resource, that is, the PRACH resource selected by the source cell from the first PRACH resource set provided by the target cell, then the target cell is not clear about the identity of the terminal device. The source cell can send the first TAT to the target cell after the target cell notifies the source cell of the first TA as described above, and the target cell can start the first TAT. The source cell may also send the first TAT to the target cell in a handover preparation message, and after the target cell notifies the source cell of the first TA, the source cell determines the identity of the terminal device and notifies the target cell of the identity document (ID) of the terminal device. The target cell determines the first TAT value of the terminal device based on the terminal device ID and starts the first TAT. In addition, if the protocol specifies a default TAT value, the target cell can also start the default TAT after sending the first TA without knowing the terminal device identity.

[0106] It should be noted that the above-mentioned "random access procedure of a terminal device" can be implemented independently (i.e., it can be an independent embodiment, regardless of whether the first TAT is introduced, etc.), or the "random access procedure of a terminal device" can be combined with the relevant contents provided in other embodiments. A more specific embodiment related to the random access procedure of a terminal device is provided below. It should be understood that the following embodiment can be an independent embodiment or can be combined with the above-mentioned embodiments.

[0107] The source cell indicates the first PRACH resource to the terminal device. The first PRACH resource may be a PRACH resource dedicated to the terminal device, and therefore, the first PRACH resource may also be referred to as a first dedicated PRACH resource. The first PRACH resource may be selected by the source cell from a first PRACH resource set (or first PRACH pool) provided by the target cell, and the first PRACH resource set may be a resource set allocated by the target cell to the source cell for random access. It should be understood that the target cell does not know that the first PRACH resource is a PRACH resource dedicated to the terminal device, and the "dedicated" nature of the first PRACH resource may be guaranteed by the source cell. For example, the source cell may only allocate the first PRACH resource in the first PRACH resource set to a specific terminal device, and not to other terminal devices.

[0108] In some implementations, the first PRACH resource may be indicated by a first message, which may be, for example, a PDCCH command or a MAC CE. The first message may be used to trigger the terminal device to initiate a random access procedure.

[0109] After receiving the first message, the terminal device may initiate a random access process (such as a non-contention-based random access process) and use the first PRACH resource to send a preamble to the target cell.

[0110] In some implementations, after receiving the preamble, the target cell may establish a mapping relationship between the preamble and the CG resources allocated by the target cell.

[0111] In the related art, after the target cell allocates uplink resources to the terminal device, it is not clear how long the uplink resources are valid, which may lead to unreliable communication (for example, the terminal device transmits uplink data on invalid uplink resources, and the network device cannot receive the uplink data). To address this problem, in some implementations, the validity period of the uplink resources (such as the CG resources mentioned above) allocated by the target cell to the terminal device can be defined as valid during the operation of the first TAT. By clarifying the validity period of the uplink resources allocated by the target cell to the terminal device, the reliability of communication can be improved. For example, if the target cell allocates uplink resources (such as CG resources) to the terminal device, before the first TAT times out, the terminal device believes that the uplink resources allocated by the target cell are available. Assuming that there are available CG resources before the first TAT times out, the terminal device can use the CG resources to transmit the first uplink data. If there are no available CG resources before the first TAT times out, once the first TAT times out, the CG allocated by the target cell is no longer valid.

[0112] In some implementations, if the target cell allocates a PDCCH monitoring space for the terminal device, the validity period of the PDCCH monitoring space can also be defined as valid during the first TAT. By clarifying the validity period of the PDCCH monitoring space allocated by the target cell to the terminal device, communication reliability can be improved. For example, if the target cell allocates a PDCCH monitoring space for the terminal device, the terminal device needs to monitor the PDCCH of the target cell to obtain the DG before the first TAT expires. If the terminal device does not obtain the DG before the first TAT expires, the PDCCH monitoring space allocated by the target cell is no longer valid.

[0113] In some implementations, if the target cell configures both CG resources and PDCCH monitoring space for the terminal device, the terminal device can use the first CG resource or DG (determined based on the PDCCH monitoring space) to transmit the first uplink data before the first TAT expires. If the terminal device does not complete the transmission of the first uplink data before the first TAT expires, the CG resource and PDCCH monitoring space are no longer valid.

[0114] In some implementations, if the CG resources and PDCCH monitoring space configured by the target cell for the terminal device are no longer valid, the terminal device can execute the handover failure related process. For example, if the first TAT times out and the terminal device has not successfully accessed the target cell, the terminal device can initiate contention-based random access to the target cell that performs the underlying fast handover. If the terminal device has acquired the TA of a part of the quasi-target cells in advance, and maintains the TATs corresponding to the TAs of these quasi-target cells, and there are TATs that have not timed out among these TATs, the terminal device can try to access these quasi-target cells. For example, the terminal device can directly send the first uplink data block to the quasi-target cell through CG or DG, or it can initiate contention-based random access.

[0115] In some implementations, if the CG resources or PDCCH monitoring space allocated by the target cell to the terminal device is no longer valid, the target cell does not delete the CG resources or PDCCH monitoring space configured for the terminal device. When the TAT corresponding to the terminal device is started again, the target cell considers that the CG resources or PDCCH monitoring space allocated to the terminal device is effective again.

[0116] In the related art, when the source cell triggers the terminal device to initiate random access to the target cell to obtain the TA in advance, how to determine and who determines whether the random access is successful is not clear. To address this issue, after sending a first message to the terminal device (the first message is used to trigger the terminal device to initiate a random access process), the source cell can start a first timer. If the first TA is received during the operation of the first timer, the source cell determines that the random access process is successful; if the first TA is not received during the operation of the first timer, the source cell determines that the random access process has failed. If the source cell determines that the random access process has failed, the source cell can trigger the terminal device to initiate random access to the target cell again. The value of the first timer is determined by the implementation algorithm of the source base station. The specific value is related to the message interaction time between cells and the PRACH resource density of the target cell. Based on the first timer, the source cell can effectively determine whether the random access process it triggered is successful, which helps to improve the efficiency of the terminal device switching cells.

[0117] Furthermore, the first message may include one or more of the following information: an offset value of the transmission power of the random access message; information indicating whether the terminal device needs to maintain the number of random access attempts. For example, the first information may include an offset value of the transmission power of the random access message. The terminal device may calculate the initial power for sending the preamble based on the path loss between itself and the target cell, and then add the power offset value notified in the first message as the power for sending the preamble. If a random access is unsuccessful, the source cell will increase the power offset value when triggering random access again. If the terminal device does not maintain a "random access counter", each calculation of the power for sending the preamble is equivalent to adding a different power offset value to the benchmark of an open-loop calculation. For another example, the first information may also include information indicating whether the terminal device needs to maintain the number of random access attempts. If so, the terminal device maintains the number of random access attempts; if not, the network side is responsible for maintaining the number of random access attempts. Furthermore, it is possible to explicitly indicate whether the terminal device needs to maintain the number of random access attempts, for example, using 1 to indicate that the terminal device needs to maintain the number of random access attempts, and using 0 to indicate that the terminal device does not need to maintain the number of random access attempts; it is also possible to implicitly indicate that if the source cell instructs the terminal device to send a preamble in other cells, the terminal device believes that it does not need to maintain the number of random access attempts; if the source cell instructs the terminal device to send a preamble in this cell, the terminal device itself needs to maintain the number of random access attempts.

[0118] Furthermore, the source cell may count the total number of random access attempts made by the terminal device in each target cell, that is, the number of attempts before random access is successful. The source cell may indicate the number of random access attempts made by the terminal device to the target cell so that the target cell can adjust its random access-related configuration parameters.

[0119] After a terminal device successfully initiates random access to a target cell, the source cell may send a low-level fast handover instruction to the terminal device, instructing the terminal device to switch to the target cell. Based on the terminal device's measurement results, the source cell may determine whether to trigger a low-level fast handover. If a handover is determined, an instruction is sent to the terminal device. Furthermore, the instruction may be a MAC CE or downlink control information (DCI).

[0120] The cell handover method of the embodiment of the present application is illustrated below with reference to Figure 6. As shown in Figure 6, the process of performing cell handover by the terminal device can be divided into five stages, namely, random resource pool allocation stage, handover preparation stage, pre-TA acquisition stage, handover indication stage, and TAT running stage.

[0121] Random resource pool allocation phase

[0122] In step S601, the target cell allocates a random access resource pool to the source cell. If a UE in the source cell needs to switch to the target cell, it can initiate a random access procedure to the target cell using one of the resources in the random access resource pool. The random access resource pool is public and is used by all UEs that may switch from the source cell to the target cell. Therefore, it can be allocated when the connection between base stations is established, or it can be allocated later.

[0123] Switching preparation phase

[0124] In step S602, the source cell notifies the target cell of the UE's TAT ​​value in a Handover Prepare message. When the UE initiates random access to the target cell to obtain the TA, the target cell can use the TAT to determine the TA's validity period. The source cell can also notify the target cell of the UE's TAT ​​value in other steps following the Handover Prepare message. For example, in step S609 shown in Figure 6, after the target cell notifies the source cell of the TA, the source cell then notifies the target cell of the UE's TAT ​​value.

[0125] After receiving the Handover Preparation message, the target cell performs admission control for the UE and, in the Handover Preparation Complete message of step S603, notifies the source cell of information such as the C-RNTI, CG resources, PDCCH monitoring space CORESET, and SR allocated to the UE. The target cell may also perform only admission control and not notify the source cell of the above information in the Handover Preparation Complete message. Instead, the target cell may wait until the UE successfully acquires the TA in advance before notifying the source cell of this information. For example, in the step of notifying the TA in step S608, or in step S610 after the TAT notification step, a notification message "UE Information Indication" is added from the target cell to the source cell to notify the source cell of this information. The target cell may also disperse this information in the "Handover Preparation Complete" message and the "UE Information Indication" message after the TAT indication. The information can be freely combined to determine which information is placed in the "Handover Preparation Complete" message and which is placed in the "UE Information Indication" message.

[0126] In step S604, after the source cell receives the handover preparation completion message from the target cell, it sends a handover configuration message to the UE. The handover configuration message must include the Cell ID of the target cell, but other information may not be included. Even if the target cell includes the above information of the UE in the handover preparation completion message, the source cell can provide all of the above information to the UE, or only provide part of the information to the UE. For example, in step S604, the source cell only includes the C-RNTI allocated by the target cell to the UE in the handover configuration message. If the source cell only provides part of the above information to the UE in the handover configuration message, the other information can be provided to the UE through the L1 / L2 handover indication in step S612.

[0127] In step S605, after receiving the handover configuration, the UE replies with a "handover configuration response" message to the source cell, indicating that it has successfully received the handover configuration message.

[0128] Pre-acquisition TA stage

[0129] The UE obtains its own TA in the target cell in advance through random access. The UE can obtain the TA through contention-based random access or through non-contention-based random access. The optional random access methods of the UE can be seen in Figure 5. As an example, in step S606, the UE receives the PDCCH order of the source cell. The order instructs the UE to trigger a non-contention random access process based on part of the resources in the random access resource pool, that is, based on the first dedicated PRACH resource trigger. Part of the resources in the random access resource pool are specially allocated to the current UE by the source cell, and the source cell will no longer allocate this part of the resources to other UEs. Therefore, this resource is equivalent to being dedicated to the current UE, avoiding contention between UEs.

[0130] Based on the PDCCH order of the source cell, in step S607, the UE sends a preamble to the target cell on the above resources.

[0131] After receiving the preamble, the target cell calculates the TA value of the UE and may notify the source cell or the UE of the TA value. As an example, in step S608, the target cell notifies the source cell of the TA value of the UE and starts the TAT of the UE. The TA value of the UE is valid during the running time of the TAT.

[0132] After receiving the TA value, the source cell starts the TAT for the UE. The TA value of the UE is valid during the TAT running time. After the UE completes the measurement report in step S611, the source cell indicates the TA value and the remaining duration of the TAT started by the source cell to the UE through an L1 / L2 handover instruction in step S612.

[0133] After receiving the TA value and the remaining duration of the TAT, the UE may start a timer based on the remaining duration of the TAT, and the TA value is valid during the running time of the timer.

[0134] In addition, after triggering the UE to initiate random access, the source cell can start a timer. If the corresponding TA notification is received from the target cell, the timer is stopped. If the timer times out and the corresponding TA notification is still not received from the target cell, the source cell considers that the random access has failed and can trigger the UE to initiate random access to the target cell again.

[0135] The source cell can also notify the UE of a power offset value through a PDCCH order when triggering a random access. The UE can calculate the initial preamble power based on the path loss between itself and the target cell and add the power offset value notified in the PDCCH order to the preamble power. If the random access attempt fails, the source cell will increase the power offset value when triggering the next random access attempt.

[0136] The source cell may also notify the UE to maintain its random access attempt count through the PDCCH order when triggering the UE to initiate random access, for example, by using the number 1 to indicate that the UE needs to maintain the random access count for this random access, and by using the number 0 to indicate that the UE does not need to maintain the random access count for this random access.

[0137] Indication switching phase

[0138] After successful random access, the source cell sends a low-level fast handover instruction to the UE, instructing the UE to switch to the target cell. Based on the UE's measurement results, the source cell determines whether to trigger low-level fast handover. If a switch is determined, the source cell sends an instruction to the UE, as shown in step S612. This instruction can be a MAC CE or a DCI.

[0139] TAT operation phase

[0140] After the TAT is started, if the TAT does not expire, or if the timer started by the UE does not expire, the TA value obtained by the UE through random access can be considered valid. Furthermore, if the TA or the timer started by the UE does not expire, the resources allocated to the UE by the target cell can also be considered valid, and the UE can upload uplink data blocks to the target cell using these resources.

[0141] Specifically, if CG resources are allocated during the handover preparation phase, the UE considers that the CG is available before the TAT times out. If the handover preparation phase instructs monitoring PDCCH to obtain DG, the UE considers that it needs to monitor the PDCCH of the target cell before the TAT times out to obtain DG. If there is a CG before the TAT times out, the UE uses the CG to send uplink data blocks. If the UE monitors the DG allocated to it by the target cell before the TAT times out, it uses the DG to send uplink data blocks. If the target cell is configured with both CG and PDCCH monitoring during the handover preparation phase, the UE will use whichever resource arrives first before the TAT times out.

[0142] After the TAT is started, if the TAT times out or the timer started by the UE times out before the UE successfully accesses the target cell, the TA obtained by the UE and the resources allocated to the UE by the target device are considered invalid. At this time, the UE performs the handover failure step and can initiate contention-based random access to the target cell.

[0143] In the above-mentioned process of terminal device switching cells, the TAT can be used to determine the effective time of the TA obtained by the UE and the resources allocated to the UE by the target cell. The timer started by the source cell can be used to determine whether the non-competitive random access triggered by the source cell is successful, thereby improving the reliability of communication.

[0144] The method embodiment of the present application is described in detail above in conjunction with Figures 1 to 6 , and the device embodiment of the present application is described in detail below in conjunction with Figures 7 to 10 . It should be understood that the description of the method embodiment corresponds to the description of the device embodiment, and therefore, for portions not described in detail, reference can be made to the above method embodiment.

[0145] FIG7 is a schematic diagram of the structure of a terminal device provided in an embodiment of the present application. The terminal device 700 in FIG7 includes a receiving module 710. The receiving module 710 is configured to receive a first TA during an L1 / L2 handover process. The first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0146] In some implementations, the receiving module 710 is also used to receive first configuration information, and the first configuration information is used to indicate one or more of the following information: C-RNTI allocated by the target cell to the terminal device; CG resources allocated by the target cell to the terminal device; PDCCH monitoring space allocated by the target cell to the terminal device; dedicated PRACH resources allocated by the target cell to the terminal device; SR configuration.

[0147] In some implementations, the CG resources or PDCCH monitoring space are valid during the operation of the first TAT.

[0148] In some implementations, if the first configuration information only indicates CG resources, the first uplink data of the terminal device in the target cell is transmitted through the CG resources; or, if the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the DG, and the DG is determined based on the PDCCH monitoring space; or, if the first configuration information indicates CG resources and PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the first uplink resource, and the first uplink resource is the uplink resource selected by the terminal device from the CG resources and the DG, or the first uplink resource is the uplink resource with an earlier transmission time among the CG resources and the DG.

[0149] In some implementations, part or all of the information in the first configuration information is carried in a handover configuration message sent by the source cell.

[0150] In some implementations, the first TA is determined based on a random access process initiated by the terminal device, and the random access process is a contention-based random access process or a non-contention-based random access process.

[0151] In some implementations, the random access process is a contention-based random access process, and the contention-based random access process is triggered by a source cell, a target cell, or the terminal device itself.

[0152] In some implementations, the source cell triggering includes: the source cell triggering based on a handover configuration message, the source cell triggering based on a MAC CE, or the source cell triggering based on a PDCCH command; or, the target cell triggering includes: the target cell triggering based on a MAC CE, or the target cell triggering based on a PDCCH command.

[0153] In some implementations, the random access procedure is a non-contention-based random access procedure, and the non-contention-based random access procedure is triggered by a source cell or a target cell.

[0154] In some implementations, the non-contention-based random access procedure is triggered by a source cell, and the non-contention-based random access procedure is initiated based on a first dedicated PRACH resource, and the first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell.

[0155] In some implementations, the non-contention-based random access procedure is triggered by a source cell, and the non-contention-based random access procedure is initiated based on a second dedicated PRACH resource, and the second dedicated PRACH resource is allocated to the terminal device by the target cell.

[0156] In some implementations, the source cell triggering includes: the source cell being triggered by a PDCCH command, or the source cell being triggered by a handover configuration message.

[0157] In some implementations, the running time of the first TAT is determined based on the remaining time of the first TAT indicated by the source cell.

[0158] In some implementations, the receiving module 710 is also used to receive a first message sent by the source cell, where the first message is used to trigger the terminal device to initiate a random access process, and the first message includes one or more of the following information: an offset value of the transmission power of the random access message; information indicating whether the terminal device needs to maintain the number of random access attempts.

[0159] Figure 8 is a schematic diagram of the structure of a network device provided by one embodiment of the present application. The network device 800 shown in Figure 8 is a network device corresponding to a source cell and includes a transceiver module 810. Transceiver module 810 is configured to receive a first TA during an L1 / L2 handover. The first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

[0160] In some implementations, the first TAT is started after the source cell receives the first TA; or, the first TAT is started after the source cell receives the first TA and sends the first TAT to the target cell.

[0161] In some implementations, the network device further includes a start module, which is used to start a first timer after sending a first message, and the first message is used to trigger the terminal device to initiate a random access process; if a first TA is received during the operation of the first timer, the source cell determines that the random access process is successful; and / or if the first TA is not received during the operation of the first timer, the source cell determines that the random access process has failed.

[0162] In some implementations, the transceiver module 810 is also used for the source cell to receive first configuration information from the target cell; or, the source cell sends first configuration information to the terminal device; wherein the first configuration information is used to indicate one or more of the following information: the C-RNTI allocated by the target cell to the terminal device; the CG resources allocated by the target cell to the terminal device; the PDCCH monitoring space allocated by the target cell to the terminal device; the dedicated PRACH resources allocated by the target cell to the terminal device; and the SR configuration.

[0163] In some implementations, the CG resources or PDCCH monitoring space are valid during the operation of the first TAT.

[0164] In some implementations, if the first configuration information only indicates CG resources, the first uplink data of the terminal device in the target cell is transmitted through the CG resources; or, if the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the DG, and the DG is determined based on the PDCCH monitoring space; or, if the first configuration information indicates CG resources and PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the first uplink resource, and the first uplink resource is the uplink resource selected by the terminal device from the CG resources and the DG, or the first uplink resource is the uplink resource with an earlier transmission time among the CG resources and the DG.

[0165] In some implementations, the first TA is determined based on a random access process initiated by the terminal device, and the random access process is a contention-based random access process or a non-contention-based random access process.

[0166] In some implementations, the random access process is a contention-based random access process, and the contention-based random access process is triggered by a source cell, a target cell, or the terminal device itself.

[0167] In some implementations, the source cell triggering includes: the source cell triggering based on a handover configuration message, the source cell triggering based on a MAC CE, or the source cell triggering based on a PDCCH command; or, the target cell triggering includes: the target cell triggering based on a MAC CE, or the target cell triggering based on a PDCCH command.

[0168] In some implementations, the random access procedure is a non-contention-based random access procedure, and the non-contention-based random access procedure is triggered by a source cell or a target cell.

[0169] In some implementations, the non-contention-based random access procedure is triggered by a source cell, and the non-contention-based random access procedure is initiated based on a first dedicated PRACH resource, and the first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell.

[0170] In some implementations, the non-contention-based random access procedure is triggered by a source cell, and the non-contention-based random access procedure is initiated based on a second dedicated PRACH resource, and the second dedicated PRACH resource is allocated to the terminal device by the target cell.

[0171] In some implementations, the source cell triggering includes: the source cell being triggered by a PDCCH command, or the source cell being triggered by a handover configuration message.

[0172] In some implementations, the running time of the first TAT is determined based on the remaining time of the first TAT indicated by the source cell.

[0173] In some implementations, the transceiver module 810 is also used to send a first message to the terminal device, where the first message is used to trigger the terminal device to initiate a random access process, and the first message includes one or more of the following information: an offset value of the transmission power of the random access message; information indicating whether the terminal device needs to maintain the number of random access attempts.

[0174] Figure 9 is a schematic diagram of the structure of a network device provided in another embodiment of the present application. The network device 900 shown in Figure 9 is a network device corresponding to a target cell and includes a transceiver module 910. Transceiver module 910 is configured to transmit a first TA during an L1 / L2 handover. The first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation of the first TAT of the terminal device.

[0175] In some implementations, the first TAT is started after the target cell sends the first TA; or, the first TAT is started after the target cell sends the first TA to the source cell and receives the first TAT sent by the source cell.

[0176] In some implementations, the transceiver module 910 is also used to send first configuration information to the source cell, and the first configuration information is used to indicate one or more of the following information: the C-RNTI allocated by the target cell to the terminal device; the CG resources allocated by the target cell to the terminal device; the PDCCH monitoring space allocated by the target cell to the terminal device; the dedicated PRACH resources allocated by the target cell to the terminal device; and the SR configuration.

[0177] In some implementations, the CG resources or PDCCH monitoring space are valid during the operation of the first TAT.

[0178] In some implementations, if the first configuration information only indicates CG resources, the first uplink data of the terminal device in the target cell is transmitted through the CG resources; or, if the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the DG, and the DG is determined based on the PDCCH monitoring space; or, if the first configuration information indicates CG resources and PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the first uplink resource, and the first uplink resource is the uplink resource selected by the terminal device from the CG resources and the DG, or the first uplink resource is the uplink resource with an earlier transmission time among the CG resources and the DG.

[0179] In some implementations, the first TA is determined based on a random access process initiated by the terminal device, and the random access process is a contention-based random access process or a non-contention-based random access process.

[0180] In some implementations, the random access process is a contention-based random access process, and the contention-based random access process is triggered by a source cell, a target cell, or the terminal device itself.

[0181] In some implementations, the source cell triggering includes: the source cell triggering based on a handover configuration message, the source cell triggering based on a MAC CE, or the source cell triggering based on a PDCCH command; or, the target cell triggering includes: the target cell triggering based on a MAC CE, or the target cell triggering based on a PDCCH command.

[0182] In some implementations, the random access procedure is a non-contention-based random access procedure, and the non-contention-based random access procedure is triggered by a source cell or a target cell.

[0183] In some implementations, the non-contention-based random access procedure is triggered by a source cell, and the non-contention-based random access procedure is initiated based on a first dedicated PRACH resource, and the first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell.

[0184] In some implementations, the non-contention-based random access procedure is triggered by a source cell, and the non-contention-based random access procedure is initiated based on a second dedicated PRACH resource, and the second dedicated PRACH resource is allocated to the terminal device by the target cell.

[0185] In some implementations, the source cell triggering includes: the source cell being triggered by a PDCCH command, or the source cell being triggered by a handover configuration message.

[0186] In some implementations, the running time of the first TAT is determined based on the remaining time of the first TAT indicated by the source cell.

[0187] Figure 10 is a schematic diagram of the structure of a communication device provided in an embodiment of the present application. The communication device 1000 in Figure 10 can be used to implement the method described in the above method embodiment. The device 1000 can be a chip, a terminal device, or a base station.

[0188] The communication device 1000 may include one or more processors 1010. The processor 1010 may support the device 1000 to implement the method described in the above method embodiment. The processor 1010 may be a general-purpose processor or a special-purpose processor. For example, the processor may be a central processing unit (CPU). Alternatively, the processor may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, etc. The general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0189] The communication device 1000 may further include one or more memories 1020. The memories 1020 store programs that can be executed by the processor 1010, causing the processor 1010 to perform the methods described in the above method embodiments. The memories 1020 may be independent of the processor 1010 or integrated into the processor 1010.

[0190] The communication device 1000 may further include a transceiver 1030. The processor 1010 may communicate with other devices or chips via the transceiver 1030. For example, the processor 1010 may transmit and receive data with other devices or chips via the transceiver 1030.

[0191] It should be understood that in the embodiment of the present application, the processor 1010 can adopt a general central processing unit (CPU), a microprocessor, an application specific integrated circuit (ASIC), or one or more integrated circuits to execute relevant programs to implement the technical solutions provided in the embodiment of the present application.

[0192] The memory 1020 may include a read-only memory and a random access memory, and provides instructions and data to the processor 1010. A portion of the processor 1010 may also include a non-volatile random access memory. For example, the processor 1010 may also store information about the device type.

[0193] During implementation, each step of the above method can be completed by an integrated logic circuit of the hardware in the processor 1010 or by instructions in the form of software. The method for requesting uplink transmission resources disclosed in conjunction with the embodiments of the present application can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software modules in the processor. The software module can be located in a mature storage medium in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory 1020, and the processor 1010 reads the information in the memory 1020 and completes the steps of the above method in combination with its hardware. To avoid repetition, it will not be described in detail here.

[0194] It should be understood that in the embodiment of the present application, the processor 1010 may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0195] The present application also provides a computer-readable storage medium for storing a program. The computer-readable storage medium can be applied to a terminal device or a base station provided in the present application, and the program enables a computer to execute the wireless communication method in each embodiment of the present application.

[0196] The present application also provides a computer program product. The computer program product includes a program. The computer program product can be applied to the terminal device or base station provided in the embodiments of the present application, and the program enables a computer to execute the wireless communication method in each embodiment of the present application.

[0197] The embodiments of the present application also provide a computer program. The computer program can be applied to the terminal device or base station provided in the embodiments of the present application, and the computer program enables a computer to execute the wireless communication method in each embodiment of the present application.

[0198] It should be understood that in the embodiments of the present application, "B corresponding to A" means that B is associated with A and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B based solely on A, but B can also be determined based on A and / or other information.

[0199] It should be understood that the term "and / or" in this document simply describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0200] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0201] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0202] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0203] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0204] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be read by a computer or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a digital versatile disc (DVD)), or a semiconductor medium (eg, a solid state disk (SSD)).

[0205] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

Claims

1. A cell switching method, characterized in that: include: During the layer 1 / layer 2 L1 / L2 switching process, the terminal device receives a first time advance TA, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation of the first time synchronization timer TAT of the terminal device.

2. The method according to claim 1, characterized in that: The method further comprises: The terminal device receives first configuration information, where the first configuration information is used to indicate one or more of the following information: The target cell is a cell radio network temporary identifier C-RNTI allocated to the terminal device; The target cell allocates a configuration authorization CG resource to the terminal device; The target cell is a physical downlink control channel PDCCH monitoring space allocated by the terminal device; The target cell allocates a dedicated physical random access channel PRACH resource to the terminal device; Scheduling request SR configuration.

3. The method according to claim 2, characterized in that The CG resources or the PDCCH monitoring space are valid during the operation of the first TAT.

4. The method according to claim 2 or 3, characterized in that: If the first configuration information only indicates the CG resource, the first uplink data of the terminal device in the target cell is transmitted through the CG resource; or, If the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through a dynamic scheduling DG, and the DG is determined based on the PDCCH monitoring space; or, If the first configuration information indicates the CG resources and the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the first uplink resource, and the first uplink resource is an uplink resource selected by the terminal device from the CG resources and the DG, or the first uplink resource is an uplink resource with an earlier transmission time between the CG resources and the DG.

5. The method according to any one of claims 2 to 4, characterized in that Part or all of the first configuration information is carried in a handover configuration message sent by the source cell.

6. The method according to any one of claims 1 to 5, characterized in that The first TA is determined based on a random access process initiated by the terminal device, and the random access process is a contention-based random access process or a non-contention-based random access process.

7. The method according to claim 6, characterized in that The random access process is a non-contention-based random access process, and the non-contention-based random access process is triggered by a source cell or a target cell.

8. The method according to claim 7, characterized in that The non-contention-based random access procedure is triggered by the source cell, and the non-contention-based random access procedure is initiated based on a first dedicated PRACH resource, and the first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell.

9. The method according to claim 7, characterized in that: The non-contention-based random access process is triggered by the source cell, and the non-contention-based random access process is initiated based on a second dedicated PRACH resource, and the second dedicated PRACH resource is allocated by the target cell to the terminal device.

10. The method according to any one of claims 7 to 9, characterized in that The source cell triggering includes: the source cell being triggered by a PDCCH command, or the source cell being triggered by a handover configuration message.

11. The method according to any one of claims 1 to 10, characterized in that The running time of the first TAT is determined based on the remaining time of the first TAT indicated by the source cell.

12. The method according to any one of claims 1 to 11, characterized in that The method further comprises: The terminal device receives a first message sent by a source cell, where the first message is used to trigger the terminal device to initiate a random access process, and the first message includes one or more of the following information: An offset value of the transmit power of the random access message; Indicates whether the terminal device needs to maintain information on the number of random access attempts.

13. A cell switching method, characterized in that: include: During the layer 1 / layer 2 L1 / L2 switching process, the source cell receives a first time advance TA, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation of a first time synchronization timer TAT of the terminal device.

14. The method according to claim 13, characterized in that The first TAT is started after the source cell receives the first TA; or, the first TAT is started after the source cell receives the first TA and sends the first TAT to the target cell.

15. The method according to claim 13 or 14, characterized in that The method further comprises: After sending the first message, the source cell starts a first timer, where the first message is used to trigger the terminal device to initiate a random access process; If the first TA is received during the running of the first timer, the source cell determines that the random access procedure is successful; and / or If the first TA is not received during the running of the first timer, the source cell determines that the random access procedure has failed.

16. The method according to any one of claims 13 to 15, characterized in that The method further comprises: The source cell receives first configuration information from the target cell; or, The source cell sends the first configuration information to the terminal device; The first configuration information is used to indicate one or more of the following information: The target cell is a cell radio network temporary identifier C-RNTI allocated to the terminal device; The target cell allocates a configuration authorization CG resource to the terminal device; The target cell is a physical downlink control channel PDCCH monitoring space allocated by the terminal device; The target cell allocates a dedicated physical random access channel PRACH resource to the terminal device; Scheduling request SR configuration.

17. The method according to claim 16, characterized in that The CG resources or the PDCCH monitoring space are valid during the operation of the first TAT.

18. The method according to claim 16 or 17, characterized in that: If the first configuration information only indicates the CG resource, the first uplink data of the terminal device in the target cell is transmitted through the CG resource; or, If the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through a dynamic scheduling DG, and the DG is determined based on the PDCCH monitoring space; or, If the first configuration information indicates the CG resources and the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the first uplink resource, and the first uplink resource is an uplink resource selected by the terminal device from the CG resources and the DG, or the first uplink resource is an uplink resource with an earlier transmission time between the CG resources and the DG.

19. The method according to any one of claims 13 to 18, characterized in that The first TA is determined based on a random access process initiated by the terminal device, and the random access process is a contention-based random access process or a non-contention-based random access process.

20. The method according to claim 19, characterized in that The random access process is a non-contention-based random access process, and the non-contention-based random access process is triggered by the source cell or the target cell.

21. The method according to claim 20, characterized in that The non-contention-based random access procedure is triggered by the source cell, and the non-contention-based random access procedure is initiated based on a first dedicated PRACH resource, and the first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell.

22. The method according to claim 20, characterized in that The non-contention-based random access process is triggered by the source cell, and the non-contention-based random access process is initiated based on a second dedicated PRACH resource, and the second dedicated PRACH resource is allocated by the target cell to the terminal device.

23. The method according to any one of claims 20 to 22, characterized in that The source cell triggering includes: the source cell being triggered by a PDCCH command, or the source cell being triggered by a handover configuration message.

24. The method according to any one of claims 13 to 23, characterized in that The running time of the first TAT is determined based on the remaining time of the first TAT indicated by the source cell.

25. The method according to any one of claims 13 to 24, characterized in that The method further comprises: The source cell sends a first message to the terminal device, where the first message is used to trigger the terminal device to initiate a random access process, and the first message includes one or more of the following information: An offset value of the transmit power of the random access message; Indicates whether the terminal device needs to maintain information on the number of random access attempts.

26. A cell switching method, characterized in that: include: During the layer 1 / layer 2 L1 / L2 switching process, the target cell sends a first time advance TA, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation of the first time synchronization timer TAT of the terminal device.

27. The method according to claim 26, characterized in that The first TAT is started after the target cell sends the first TA; or, the first TAT is started after the target cell sends the first TA to the source cell and receives the first TAT sent by the source cell.

28. The method according to claim 26 or 27, characterized in that The method further comprises: The target cell sends first configuration information to the source cell, where the first configuration information is used to indicate one or more of the following information: The target cell is a cell radio network temporary identifier C-RNTI allocated to the terminal device; The target cell allocates a configuration authorization CG resource to the terminal device; The target cell is a physical downlink control channel PDCCH monitoring space allocated by the terminal device; The target cell allocates a dedicated physical random access channel PRACH resource to the terminal device; Scheduling request SR configuration.

29. The method according to claim 28, characterized in that The CG resources or the PDCCH monitoring space are valid during the operation of the first TAT.

30. The method according to claim 28 or 29, characterized in that: If the first configuration information only indicates the CG resource, the first uplink data of the terminal device in the target cell is transmitted through the CG resource; or, If the first configuration information only indicates the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through a dynamic scheduling DG, and the DG is determined based on the PDCCH monitoring space; or, If the first configuration information indicates the CG resources and the PDCCH monitoring space, the first uplink data of the terminal device in the target cell is transmitted through the first uplink resource, and the first uplink resource is an uplink resource selected by the terminal device from the CG resources and the DG, or the first uplink resource is an uplink resource with an earlier transmission time between the CG resources and the DG.

31. The method according to any one of claims 26 to 30, characterized in that The first TA is determined based on a random access process initiated by the terminal device, and the random access process is a contention-based random access process or a non-contention-based random access process.

32. The method according to claim 31, characterized in that The random access process is a non-contention-based random access process, and the non-contention-based random access process is triggered by a source cell or by the target cell.

33. The method according to claim 32, characterized in that The non-contention-based random access procedure is triggered by the source cell, and the non-contention-based random access procedure is initiated based on a first dedicated PRACH resource, and the first dedicated PRACH resource is selected by the source cell from a first PRACH resource set provided by the target cell.

34. The method according to claim 32, characterized in that The non-contention-based random access process is triggered by the source cell, and the non-contention-based random access process is initiated based on a second dedicated PRACH resource, and the second dedicated PRACH resource is allocated by the target cell to the terminal device.

35. The method according to any one of claims 32 to 34, characterized in that The source cell triggering includes: the source cell being triggered by a PDCCH command, or the source cell being triggered by a handover configuration message.

36. The method according to any one of claims 26 to 35, characterized in that The running time of the first TAT is determined based on the remaining time of the first TAT indicated by the source cell.

37. A terminal device, characterized in that: include: The receiving module is used to receive a first TA during the L1 / L2 switching process, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

38. A network device, characterized in that: The network device is a network device corresponding to the source cell, and the device includes: The transceiver module is used to receive a first TA during the L1 / L2 switching process, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

39. A network device, characterized in that: The network device is a network device corresponding to the target cell, and the device includes: The transceiver module is used to send a first TA during the L1 / L2 switching process, where the first TA is the TA of the terminal device relative to the target cell, and the first TA is valid during the operation period of the first TAT of the terminal device.

40. A terminal device, characterized in that: It comprises a transceiver, a memory and a processor, wherein the memory is used to store programs, and the processor is used to call the programs in the memory and control the transceiver to receive or send signals so that the terminal device executes the method as described in any one of claims 1 to 12.

41. A network device, characterized in that: It comprises a transceiver, a memory and a processor, wherein the memory is used to store programs, and the processor is used to call the programs in the memory and control the transceiver to receive or send signals so that the network device executes the method as described in any one of claims 13-25.

42. A network device, characterized in that: It comprises a transceiver, a memory and a processor, wherein the memory is used to store programs, and the processor is used to call the programs in the memory and control the transceiver to receive or send signals so that the network device executes the method as described in any one of claims 26-36.

43. A device, characterized in that It comprises a processor, which is used to call a program from a memory so that the device executes the method as described in any one of claims 1-12, 13-25 or 26-36.

44. A chip, characterized in that: It comprises a processor, which is used to call a program from a memory, so that a device equipped with the chip executes the method as described in any one of claims 1-12, 13-25 or 26-36.

45. A computer-readable storage medium, characterized in that A program is stored thereon, the program causing a computer to execute the method according to any one of claims 1-12, 13-25 or 26-36.

46. ​​A computer program product, characterized in that A program is included, which causes a computer to execute the method as described in any one of claims 1-12, 13-25 or 26-36.

47. A computer program, characterized in that The computer program causes a computer to execute the method of any one of claims 1-12, 13-25 or 26-36.

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