Cell handover method and communication apparatus

Abstract

The present application relates to the field of communications, and in particular to a cell handover method and a communication apparatus. In a carrier aggregation scenario, a terminal can change a secondary cell used for communication. In general, the change of the secondary cell needs to be achieved by means of secondary cell activation after primary cell handover, the process from the start of primary cell handover to the completion of secondary cell activation requires a relatively long time period, and during this time period, the terminal cannot use carrier aggregation for communication, causing adverse impact on user experience. In the method provided by the present application, the information for triggering primary cell handover can also be used for triggering secondary cell handover, so that the secondary cell handover can be performed synchronously with the primary cell handover; and compared with a method of activating a secondary cell after the completion of primary cell handover, the method provided by the present application can reduce the delay of changing a secondary cell.

Description

Method and communication device for switching cells

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 30, 2023, with application number 202311637519.6 and application name “Method and communication device for switching cells”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communications, and in particular to a method and a communication device for switching cells. Background Art

[0003] Carrier aggregation (CA) is a technology that increases transmission bandwidth, integrates multiple frequency domain resources, and improves resource utilization. In CA, a terminal's serving cell includes a primary cell (PCell) and a secondary cell (SCell). The component carrier (CC) corresponding to the primary cell is called a primary component carrier (PCC), and the CC corresponding to the secondary cell is called a secondary component carrier (SCC). CA can aggregate a PCC and at least one SCC for use by the terminal.

[0004] CA supports the aggregation of 16 CCs, and a terminal can use only some of these CCs. In this case, if the traffic volume of the active CC is high or the channel status is poor, the terminal can switch the CC in use, that is, switch cells. Cell switching requires operations such as time synchronization and channel measurement, and takes a certain amount of time to complete the cell switching. How to reduce the latency of cell switching is currently an issue that needs to be addressed. Summary of the Invention

[0005] Embodiments of the present application provide a method for switching cells, a communication device, a computer-readable storage medium, and a computer program product, which can reduce the delay of cell switching.

[0006] In a first aspect, an embodiment of the present application provides a method for switching cells. The method may be performed by a terminal or a chip applied to the terminal. The following description uses the terminal as an example. The method is applied to a terminal, wherein the serving cell of the terminal includes a first primary cell and a first secondary cell. The method includes: receiving first information instructing the terminal to switch the primary cell from the first primary cell to the second primary cell, the first information including an identifier of the second secondary cell; and switching the primary cell from the first primary cell to the second primary cell, and switching the secondary cell from the first secondary cell to the second secondary cell according to the first information.

[0007] In this method, in addition to being used to trigger the switching of the primary cell, the first information is also used to trigger the switching of the secondary cell, so that the switching of the secondary cell can be carried out synchronously with the switching of the primary cell. Compared with the method of waiting for the completion of the switching of the primary cell and then activating the secondary cell, this method can reduce the delay of the secondary cell switching.

[0008] Optionally, before switching from the first secondary cell to the second secondary cell according to the first information, the method further includes: receiving a downlink synchronization signal of the second secondary cell; and performing a cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

[0009] Optionally, performing a cell search according to a downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell includes: before receiving the first information, performing a cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

[0010] Downlink synchronization can be performed before receiving the first information. For example, the terminal can receive the synchronization signal of the candidate secondary cell to complete downlink synchronization. After receiving the first information, downlink synchronization may no longer be performed, thereby reducing the delay of secondary cell switching.

[0011] Optionally, before switching from the first secondary cell to the second secondary cell, the method further includes: receiving a reference signal of the second secondary cell; and sending channel state information, where the channel state information is determined based on the reference signal.

[0012] Optionally, sending the channel state information includes: sending the channel state information before receiving the first information.

[0013] Channel state measurement can be performed before receiving the first information. For example, the terminal can receive the reference signal of the candidate secondary cell and complete the channel state measurement. After receiving the first information, the channel state measurement can no longer be performed, thereby reducing the delay of the secondary cell switching.

[0014] Optionally, before receiving the first information, the method further includes: sending second information, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

[0015] The simultaneous switching of the primary cell and the secondary cell requires the support of the terminal's capabilities. Some terminals may not have this capability. Therefore, the terminal reports in advance that it has the ability to simultaneously switch the primary cell and the secondary cell, and then performs the secondary cell switching based on the first information. This can avoid the failure of the secondary cell switching caused by the terminal that does not have this capability performing the primary cell switching and the secondary cell switching at the same time.

[0016] Optionally, the first information further includes a cell-radio network temporary identifier (C-RNTI) of the terminal.

[0017] The terminal can obtain and store the C-RNTIs of all candidate secondary cells in advance and use the C-RNTI of the target secondary cell after the secondary cell handover is complete. However, this method will increase signaling overhead. In this method, the first information carries the C-RNTI of the target secondary cell, eliminating the need to obtain and store the C-RNTIs of all candidate secondary cells in advance, thereby reducing signaling overhead during the secondary cell handover process.

[0018] Optionally, the first information further includes an identifier of a second primary cell, and the identifier of the second primary cell is the same as the identifier of the first primary cell.

[0019] The second primary cell identifier is the same as the first primary cell identifier, and the terminal can understand that there is no need to perform primary cell switching, only secondary cell switching. This implementation reuses the existing primary cell switching process to achieve the function of switching to a separate secondary cell, which has better forward compatibility.

[0020] In a second aspect, an embodiment of the present application provides a method for switching cells, wherein the execution subject of the method may be a base station or a chip applied to a base station, and the following description is based on the example of the execution subject being a base station. The method comprises: sending first information, wherein the first information instructs a terminal to switch a primary cell from a first primary cell to a second primary cell, wherein the first information includes an identifier of a second secondary cell, and wherein the first information further instructs the terminal to switch a secondary cell from the first secondary cell to the second secondary cell, wherein the first primary cell and the first secondary cell are serving cells of the terminal; switching the primary cell from the first primary cell to the second primary cell, and switching the secondary cell from the first secondary cell to the second secondary cell.

[0021] The method of the second aspect corresponds to the method of the first aspect. The beneficial effects of each embodiment of the second aspect can refer to the beneficial effects of the corresponding embodiments in the first aspect and will not be repeated here.

[0022] Optionally, the method further includes: sending a downlink synchronization signal of a second secondary cell.

[0023] Optionally, sending a downlink synchronization signal of the second secondary cell includes: sending a downlink synchronization signal of the second secondary cell before sending the first information.

[0024] Optionally, the method further includes: sending a reference signal of the second secondary cell; and receiving channel state information, where the channel state information is determined based on the reference signal.

[0025] Optionally, sending the reference signal of the second secondary cell includes: sending the reference signal of the second secondary cell before sending the first information.

[0026] Optionally, before sending the first information, the method further includes: receiving second information, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

[0027] Optionally, the first information also includes the C-RNTI of the terminal.

[0028] Optionally, the first information further includes an identifier of a second primary cell, and the identifier of the second primary cell is the same as the identifier of the first primary cell.

[0029] In a third aspect, embodiments of the present application provide another method for switching cells. This method may be performed by a terminal or a chip used in a terminal. The following description uses the terminal as an example. The method includes: receiving third information instructing the terminal to switch a secondary cell from a first secondary cell to a second secondary cell; and switching the secondary cell from the first secondary cell to the second secondary cell based on the third information.

[0030] In this method, the handover process for the secondary cell is decoupled from the handover process for the primary cell. The terminal performs the handover of the secondary cell according to the third information, without having to pay attention to whether the primary cell has been switched. Compared to the method of waiting for the primary cell handover to complete before activating the secondary cell, this method can reduce the delay of the secondary cell handover.

[0031] Optionally, before switching the secondary cell from the first secondary cell to the second secondary cell according to the third information, the method further includes: receiving a downlink synchronization signal of the second secondary cell; and performing a cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

[0032] Optionally, receiving a downlink synchronization signal of the second secondary cell includes: receiving a downlink synchronization signal of the second secondary cell before receiving the third information.

[0033] Downlink synchronization can be performed before receiving the third information. For example, the terminal can receive the synchronization signal of the candidate secondary cell and complete downlink synchronization. After receiving the third information, downlink synchronization may no longer be performed, thereby reducing the delay of secondary cell switching.

[0034] Optionally, before switching the secondary cell from the first secondary cell to the second secondary cell according to the third information, the method further includes: receiving a reference signal of the second secondary cell; and sending channel state measurement information, where the channel state measurement information is determined based on the reference signal.

[0035] Optionally, receiving the reference signal of the second secondary cell includes: receiving the reference signal of the second secondary cell before receiving the third information.

[0036] Channel state measurement can be performed before receiving the third information. For example, the terminal can receive the reference signal of the candidate secondary cell and complete the channel state measurement. After receiving the third information, the channel state measurement can no longer be performed, thereby reducing the delay of the secondary cell switching.

[0037] Optionally, the third information includes the C-RNTI of the terminal.

[0038] The terminal can obtain and store the C-RNTIs of all candidate secondary cells in advance and use the C-RNTI of the target secondary cell after the secondary cell handover is complete. However, this method will increase signaling overhead. In this method, the third information carries the C-RNTI of the target secondary cell, eliminating the need to obtain and store the C-RNTIs of all candidate secondary cells in advance, thereby reducing signaling overhead during the secondary cell handover process.

[0039] Fourthly, embodiments of the present application provide another method for switching cells. This method may be performed by a base station or a chip used in a base station. The following description uses the base station as an example. The method includes: sending third information instructing a terminal to switch a secondary cell from a first secondary cell to a second secondary cell; and switching the secondary cell from the first secondary cell to the second secondary cell.

[0040] The method of the fourth aspect corresponds to the method of the third aspect. The beneficial effects of each embodiment of the fourth aspect can refer to the beneficial effects of the corresponding embodiments in the third aspect and will not be repeated here.

[0041] Optionally, the method further includes: sending a downlink synchronization signal of a second secondary cell.

[0042] Optionally, sending the downlink synchronization signal of the second secondary cell includes: sending the downlink synchronization signal of the second secondary cell before sending the third information.

[0043] Optionally, the method further includes: sending a reference signal of the second secondary cell; and receiving channel state measurement information, where the channel state measurement information is determined based on the reference signal.

[0044] Optionally, sending the reference signal of the second secondary cell includes: sending the reference signal of the second secondary cell before sending the third information.

[0045] Optionally, the third information includes the C-RNTI of the terminal.

[0046] In a fifth aspect, embodiments of the present application provide a communication device. The communication device may include a processing unit and a transceiver unit, configured to perform: any of the methods in the first aspect and its optional embodiments described above, or any of the methods in the third aspect and its optional embodiments described above. The transceiver unit is a sending unit when performing the sending step, and is a receiving unit when performing the receiving step.

[0047] In a sixth aspect, embodiments of the present application provide a communication device. The communication device may include a processing unit and a transceiver unit, configured to perform: any of the methods in the second aspect and its optional embodiments described above, or any of the methods in the fourth aspect and its optional embodiments described above. The transceiver unit is a sending unit when performing the sending step, and is a receiving unit when performing the receiving step.

[0048] In a seventh aspect, embodiments of the present application provide a communication device, which may be a terminal or a chip applied to a terminal. The communication device may include a processor configured to execute: any method in the first aspect and its optional embodiments, or any method in the third aspect and its optional embodiments.

[0049] Optionally, the communication device may further include a transceiver. When the communication device is a terminal, the transceiver may be a transceiver circuit, an antenna, etc.; when the communication device is a chip applied to a terminal, the transceiver may be an input / output interface, a pin, a circuit, etc.

[0050] Optionally, the communication device may further include a memory for storing computer programs or instructions, and the processor executes the computer programs or instructions stored in the memory to cause the communication device to perform any of the methods in the first aspect and its optional embodiments described above, or to cause the communication device to perform any of the methods in the third aspect and its optional embodiments described above. When the communication device is a terminal, the memory may be a read-only memory, a random access memory, or the like; when the communication device is a chip applied to a terminal, the memory may be a register, a cache, or the like.

[0051] In an eighth aspect, an embodiment of the present application provides a communication device, which may be a base station or a chip applied to a base station. The communication device may include a processor for executing: any method in the second aspect and its optional embodiments, or any method in the fourth aspect and its optional embodiments.

[0052] Optionally, the communication device may further include a transceiver. When the communication device is a base station, the transceiver may be a transceiver circuit, an antenna, etc.; when the communication device is a chip used in a base station, the transceiver may be an input / output interface, a pin, a circuit, etc.

[0053] Optionally, the communication device may further include a memory for storing a computer program or instruction, and the processor executes the computer program or instruction stored in the memory to cause the communication device to perform any of the methods in the second aspect and its optional embodiments, or to cause the communication device to perform any of the methods in the fourth aspect and its optional embodiments. When the communication device is a base station, the memory may be a read-only memory, a random access memory, or the like; when the communication device is a chip applied to a base station, the memory may be a register, a cache, or the like.

[0054] In the ninth aspect, an embodiment of the present application provides a communication system, which includes: the communication device described in the fifth aspect and the communication device described in the sixth aspect, or the communication device described in the seventh aspect and the communication device described in the eighth aspect.

[0055] In the tenth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed on a communication device, the communication device executes: any method in the first aspect and its optional embodiments, or any method in the second aspect and its optional embodiments, or any method in the third aspect and its optional embodiments, or any method in the fourth aspect and its optional embodiments.

[0056] In the eleventh aspect, an embodiment of the present application provides a computer program product, which includes: computer program code or computer program instructions, which, when the computer program code or computer program instructions are executed by a communication device, enable the communication device to execute: any method in the first aspect and its optional embodiments, or any method in the second aspect and its optional embodiments, or any method in the third aspect and its optional embodiments, or any method in the fourth aspect and its optional embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG1 is a schematic diagram of the architecture of a communication system used in an embodiment of the present application;

[0058] FIG2 is a schematic diagram of resource configuration for tracking reference signals provided in an embodiment of the present application;

[0059] FIG3 is a schematic diagram of a carrier aggregation scenario provided by an embodiment of the present application;

[0060] FIG4 is a schematic diagram of a cell handover scenario provided in an embodiment of the present application;

[0061] FIG5 is a schematic flowchart of a primary cell switching and secondary cell activation provided by an embodiment of the present application;

[0062] FIG6 is a schematic flowchart of a method for switching cells provided in an embodiment of the present application;

[0063] FIG7 is a schematic flowchart of a primary cell handover and a secondary cell handover provided in an embodiment of the present application;

[0064] FIG8 is a schematic flowchart of another primary cell handover and secondary cell handover provided by an embodiment of the present application;

[0065] FIG9 is a schematic flowchart of another primary cell handover and secondary cell handover provided in an embodiment of the present application;

[0066] FIG10 is a schematic diagram of a secondary cell handover scenario provided in an embodiment of the present application;

[0067] FIG11 is a schematic flowchart of another method for switching cells provided in an embodiment of the present application;

[0068] FIG12 is a schematic flowchart of a secondary cell handover provided in an embodiment of the present application;

[0069] FIG13 is a schematic flowchart of another secondary cell handover provided in an embodiment of the present application;

[0070] FIG14 is a schematic flowchart of another secondary cell handover provided in an embodiment of the present application;

[0071] FIG15 is a schematic structural diagram of a communication device provided in an embodiment of the present application;

[0072] FIG16 is a schematic structural diagram of another communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0073] Figure 1 is a schematic diagram of the architecture of a communication system 1000 used in an embodiment of the present application. As shown in Figure 1 , the communication system includes a radio access network (RAN) 100. RAN 100 includes at least one RAN node (e.g., 110a and 110b in Figure 1 , collectively referred to as 110) and may also include at least one terminal (e.g., 120a-120j in Figure 1 , collectively referred to as 120). RAN 100 may also include other RAN nodes, such as wireless relay devices and / or wireless backhaul devices (not shown in Figure 1 ). Terminal 120 is wirelessly connected to RAN node 110. Terminals and RAN nodes may be connected to each other via wired or wireless connections. Communication system 1000 may also include a core network 200. RAN node 110 is wirelessly or wiredly connected to core network 200. Core network devices in core network 200 and RAN node 110 in RAN 100 may be separate, distinct physical devices, or they may be a single physical device that integrates the logical functions of core network devices and RAN nodes. The communication system 1000 may also include the Internet 300 .

[0074] RAN100 may be an evolved universal terrestrial radio access (E-UTRA) system, a new radio (NR) system, or a future radio access system defined in the 3rd Generation Partnership Project (3GPP), or a WiFi system. RAN100 may also include two or more of the aforementioned different radio access systems. RAN100 may also be an open RAN (O-RAN).

[0075] A RAN node, also known as a network device, a radio access network device, a RAN entity or an access node, is used to help terminals access the communication system wirelessly.

[0076] In one application scenario, a RAN node may be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation NodeB (gNB) in a fifth-generation (5G) mobile communication system, a next-generation base station in a sixth-generation (6G) mobile communication system, a base station in a future mobile communication system, an access point (AP) in a WiFi system, an AP in a long-range radio (LoRa) system, or an AP in a connected vehicle system. A RAN node may be a macro base station (such as 110a in FIG. 1 ), a micro base station, an indoor station (such as 110b in FIG. 1 ), a relay node, or a donor node.

[0077] In another application scenario, multiple RAN nodes can collaborate to help terminals achieve wireless access, with different RAN nodes implementing portions of the base station's functions. For example, a RAN node can be a centralized unit (CU), a distributed unit (DU), or a radio unit (RU). The CU implements the base station's radio resource control protocol and packet data convergence protocol (PDCP) functions, as well as the service data adaptation protocol (SDAP) functions. The DU implements the base station's radio link control layer and medium access control (MAC) layer functions, as well as some or all of the physical layer functions. For detailed descriptions of each of these protocol layers, please refer to the relevant 3GPP technical specifications. The RU can be used to implement the transmission and reception of radio frequency signals. The CU and DU can be two independent RAN nodes, or they can be integrated into the same RAN node, such as in a baseband unit (BBU). The RU may be included in a radio frequency device, such as a remote radio unit (RRU), an active antenna unit (AAU), or a remote radio head (RRH). The CU may be further divided into two types of RAN nodes: the CU-control plane and the CU-user plane.

[0078] In different systems, RAN nodes may have different names. For example, in an O-RAN system, a CU may be called an open CU (O-CU), a DU may be called an open DU (O-DU), and a RU may be called an open RU (O-RU). The RAN node in the embodiments of the present application may be implemented by a software module, a hardware module, or a combination of a software module and a hardware module. For example, the RAN node may be a server loaded with the corresponding software module. The embodiments of the present application do not limit the specific technology and specific device form adopted by the RAN node. For ease of description, the following description takes a base station as an example of a RAN node.

[0079] A terminal is a device with wireless transceiver capabilities that can send and receive signals to and from a base station. It can also be referred to as a terminal device, user equipment (UE), mobile station, or mobile terminal. Terminals can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), the Internet of Things (IoT), virtual reality (VR), augmented reality (AR), industrial control, autonomous driving, telemedicine, smart grids, smart furniture, smart offices, smart wearables, smart transportation, and smart cities. The terminal may be a mobile phone (such as 120a, 120e, 120f, and 120j in FIG1 ), a tablet computer (such as 120g in FIG1 ), a printer with wireless transceiver function (such as 120h in FIG1 ), a wearable device, a vehicle (such as 120b in FIG1 ), a charging station (such as 120c in FIG1 ), an airplane (such as 120i in FIG1 ), a ship, a robot, a robotic arm, a smart home device (such as 120d in FIG1 ), etc. The embodiments of the present application do not limit the specific technology and specific device form adopted by the terminal.

[0080] As an example and not a limitation, in the embodiments of the present application, wearable devices may also be referred to as wearable smart devices, which are a general term for wearable devices that are intelligently designed and developed using wearable technology for daily wear, such as glasses, gloves, watches, clothing, and shoes. A wearable device is a portable device that is worn directly on the body or integrated into the user's clothes or accessories. Wearable devices are not just hardware devices, but also achieve powerful functions through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include electronic devices that are full-featured, large in size, and can achieve full or partial functions without relying on smartphones, such as smart watches or smart glasses, or electronic devices that only focus on a certain type of application function and need to be used in conjunction with other devices such as smartphones, such as various smart bracelets and smart jewelry for measuring vital signs.

[0081] The various terminals introduced above, if located on a vehicle (eg, placed in or installed in a vehicle), can be considered as on-board terminals, which can also be called on-board modules, on-board components, on-board chips, or on-board units (OBU).

[0082] Base stations and terminals can be fixed or mobile. They can be deployed on land, indoors or outdoors, handheld or vehicle-mounted; on water; or on aircraft, balloons, and satellites. The embodiments of this application do not limit the application scenarios of base stations and terminals.

[0083] The roles of base stations and terminals can be relative. For example, 120i in Figure 1 (which can be a helicopter or drone) can be configured as a mobile base station. For 120j accessing the wireless access network 100 via 120i, 120i is a base station; however, for 110a, 120i is a terminal. That is, communication between 110a and 120i occurs via a wireless air interface protocol. Of course, communication between 110a and 120i can also occur via a base station-to-base station interface protocol. In this case, 120i is also a base station relative to 110a. Therefore, base stations and terminals can be collectively referred to as communication devices. 110a and 110b in Figure 1 can be referred to as communication devices with base station functionality, while 120a-120j in Figure 1 can be referred to as communication devices with terminal functionality.

[0084] Communication between base stations and terminals, between base stations, and between terminals can be carried out through authorized spectrum, unauthorized spectrum, or both; communication can be carried out through spectrum below 6 gigahertz (GHz), spectrum above 6 GHz, or spectrum below 6 GHz and spectrum above 6 GHz. The embodiments of the present application do not limit the spectrum resources used for wireless communication.

[0085] In the embodiments of the present application, the functions of the base station may also be performed by a module (such as a chip) in the base station, or by a control subsystem that includes the base station functions. The control subsystem that includes the base station functions here may be a control center in the above-mentioned application scenarios such as smart grid, industrial control, smart transportation, and smart city. The functions of the terminal may also be performed by a module (such as a chip or modem) in the terminal, or by a device that includes the terminal functions.

[0086] In the embodiments of the present application, a base station sends downlink information to a terminal. This downlink information is carried on a downlink channel and is also referred to as a downlink signal. A terminal sends uplink information to a base station. This uplink information is carried on an uplink channel and is also referred to as an uplink signal. To communicate with a base station, the terminal establishes a wireless connection to a cell controlled by the base station. The cell with which the terminal establishes a wireless connection is called the serving cell of the terminal.

[0087] To facilitate understanding of the embodiments of the present application, the following briefly introduces the technologies involved in the embodiments of the present application.

[0088] 1. Time and frequency resources.

[0089] In an embodiment of the present application, data or information may be carried by time-frequency resources, wherein the time-frequency resources may include resources in the time domain and resources in the frequency domain. In the time domain, the time-frequency resources may include one or more time domain units (also referred to as time units), and in the frequency domain, the time-frequency resources may include one or more frequency domain units.

[0090] A time domain unit can be a symbol, a mini-slot, a slot, or a subframe, where the duration of a subframe in the time domain can be 1 millisecond (ms), a slot can include 7 or 14 symbols, and a mini-slot can include at least one symbol, which can be an orthogonal frequency division multiplexing (OFDM) symbol or a discrete Fourier transformation spread OFDM (DFT-s-OFDM) symbol.

[0091] A frequency domain unit can be a subcarrier, a resource block (RB), a resource block group (RBG), a subband, a precoding resource block group (PRG), a bandwidth part (BWP), a resource element (RE), a carrier, or a serving cell.

[0092] The time domain units and frequency domain units listed above are only for facilitating understanding of the embodiments of the present application and do not limit the scope of protection of the present application. The present application does not limit the specific forms of the time domain units and frequency domain units.

[0093] 2. Measurement.

[0094] Mobility management is an important component of wireless mobile communications, and measurement is its foundation. Mobility management refers to the collective term for all aspects involved in ensuring that the communication link between base stations and terminals is not interrupted due to terminal mobility.

[0095] As an optional implementation, measurements can be divided into layer 1 (L1) measurements, layer 2 (L2) measurements, and layer 3 (L3) measurements based on the layers involved. L1 measurements can also be called physical layer measurements, L2 measurements can also be called MAC layer measurements, and L3 measurements can also be called radio resource control (RRC) layer measurements. The terminal can perform specified types of measurements based on the measurement configuration.

[0096] The measurement configuration may include a measurement target, which may include, for example, a frequency point and / or a cell identifier, wherein the cell identifier may include a cell global identifier (CGI) or a physical cell identifier (PCI).

[0097] The measurement configuration may include an SSB-based measurement timing configuration (SMTC) based on a synchronization signal and physical broadcast channel block (SSB). The SMTC may include one or more of the period, length, and offset of the SSB, so that the terminal can receive the SSB according to the SMTC and perform operations such as measurements based on the SSB.

[0098] The measurement configuration may include a measurement validity period. This period may indicate the length of time the terminal needs to perform the measurement. After receiving the measurement configuration, the terminal may start a timer, the duration of which may be the measurement validity period. When the timer stops or expires, the terminal may stop performing measurements based on the parameters in the measurement configuration.

[0099] The measurement configuration may further include a measurement valid area. The measurement valid area may be indicated, for example, in the form of a cell identifier and / or an area identifier. The cell identifier may be a CGI. The area identifier may be, for example, a tracking area code (TAC) and / or a radio access network area code (RANAC). When the terminal moves outside the measurement valid area, the terminal may stop measurements based on the parameters in the measurement configuration.

[0100] For example, after the terminal obtains the measurement valid time and measurement valid area, if the terminal moves out of the measurement valid area while the timer is running, the terminal can stop the timer and stop measurement based on the parameters in the measurement configuration.

[0101] It should be understood that the parameters included in the measurement configuration listed above are examples and not limitations. The measurement configuration may include one or more parameters of the measurement valid time, measurement target, SMTC corresponding to the measurement target, and measurement valid area, and may also include other parameters.

[0102] It should be noted that the specific parameters of the above-mentioned measurement configuration can be configured through a single message or through different messages, and the embodiments of the present application are not limited to this. For example, the measurement target can be indicated in the measurement configuration carried by the system message, and the measurement validity period can be indicated in the measurement configuration carried by the RRC message (e.g., RRC release message or RRC connection release message).

[0103] It should also be noted that when a terminal receives a measurement configuration in an RRC message and a measurement configuration in a system message, the measurement configuration in the RRC message may be used preferentially. Compared to a system message, the RRC message may be referred to as dedicated signaling for transmitting the measurement configuration. In other words, the terminal may preferentially use measurement parameters obtained from the RRC message. When a parameter configured in the RRC message (e.g., a measurement target) is missing, the terminal may obtain the missing parameter from the system message.

[0104] Based on the measurement, the terminal may obtain a measurement result for the measurement target. The measurement result may include a cell identifier and / or a frequency point. Optionally, the measurement result may include the signal quality of the cell. The signal quality may include at least one of received signal code power (RSCP), reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-noise ratio (SNR), signal-to-interference plus noise ratio (SINR), reference signal strength indication (RSSI), and other signal quality information. The signal quality may be cell-level, beam-level, SSB-level, numerology-level, slice-level, or BWP-level.

[0105] The terminal may report the measurement result after accessing the cell. For example, the terminal may report the measurement result after receiving any one of an RRC setup message, an RRC resume message, an RRC connection setup message, or an RRC connection resume message.

[0106] 3. Tracking reference signal (TRS).

[0107] 3GPP defines a channel state information reference signal (CSI-RS) for tracking, which is also called a TRS.

[0108] The NR system's TRS is a specialized CSI-RS, configured via a non-zero-power Channel State Information Reference Signal Resource Set (CSI-RS Resource Set), also known as a TRS Resource Set. Each CSI-RS Resource Set contains two or four CSI-RS resources. A CSI-RS resource refers to the RE used to transmit CSI-RS on a symbol with a certain frequency domain density and bandwidth. Each CSI-RS resource has a different symbol position, but the transmission bandwidth, density, and frequency domain position are the same. As shown in Figure 2, for frequency range (FR) 1, each CSI-RS Resource Set contains four CSI-RS resources, which are located in two time slots (time slot 1 and time slot 2 corresponding to the FR1 frequency band as shown in Figure 2). The two CSI-RS resources in a time slot are separated by three symbols. For FR2, each CSI-RS Resource Set contains two CSI-RS resources, which are separated by three symbols in a time slot (time slot 1 corresponding to the FR2 frequency band as shown in Figure 2). It can be seen that the symbol position of each CSI-RS resource in the time slot is different, but the transmission bandwidth, density, and frequency domain location are the same.

[0109] There are two ways to transmit TRS. One is periodic transmission, as shown in Figure 2. Each CSI-RS Resource Set (occupying 2 or 4 symbols) represents a TRS burst in one transmission cycle. There is usually one TRS burst in one transmission cycle. The other TRS transmission method is aperiodic transmission. Aperiodic tracking reference signal (A-TRS) can be triggered by downlink control information (DCI).

[0110] TRS is mainly used for precise time and frequency synchronization of terminals. The base station will configure multiple TRS resource sets for the terminal. Each TRS resource set has a C-type quasi co-location (QCL) relationship with an SSB. That is, the terminal can first perform coarse time and frequency synchronization based on the SSB, and then use the channel parameters provided by the coarse time and frequency synchronization to receive the TRS and obtain TRS channel information. The physical downlink control channel (PDCCH) received by the terminal in the connected state has a QCL type A (QCL-TypeA) relationship with the TRS. The physical downlink shared channel (PDSCH) received by the terminal in the connected state also has a QCL-TypeA relationship with the TRS. Therefore, the TRS can provide precise time and frequency synchronization information for the PDCCH and PDSCH.

[0111] In addition to precise time and frequency synchronization, TRS can also be used by terminals to perform automatic gain control (AGC) and signal to interference ratio (SIR) estimation.

[0112] 4. Carrier aggregation.

[0113] Carrier aggregation (CA) is a technology that allows a single terminal to use multiple CCs for data transmission. This enables wide-bandwidth transmission and effectively improves uplink or downlink transmission rates. A terminal can determine the maximum number of CCs it can utilize simultaneously based on its capabilities. For example, in a three-carrier aggregation scenario, a terminal can use all three CCs simultaneously.

[0114] Figure 3 illustrates a three-carrier aggregation scenario. In this scenario, the base station provides three CCs, corresponding to cells 1, 2, and 3. A terminal establishes an RRC connection with cell 1, making cell 1 the PCell, and the CC corresponding to the PCell the PCC. During RRC reconfiguration, the terminal establishes communication connections with cells 2 and 3, which are not RRC connections. Cells 2 and 3 are then called SCells, and the CC corresponding to the SCells is the SCC. Carrier aggregation allows the PDCCH and PDSCH to be carried on different CCs, enabling cross-carrier scheduling.

[0115] The number of CCs supported by a base station is usually greater than the number of CCs supported by a terminal. For example, a base station can support carrier aggregation of 16 downlink CCs, while a terminal usually supports carrier aggregation of 2 to 3 downlink CCs. However, the terminal can select 2 to 3 downlink CCs from these 16 downlink CCs for carrier aggregation. If the currently used CC is busy or the channel conditions are poor, the terminal can switch CCs, that is, switch cells. This can not only match terminal capabilities but also achieve base station load balancing, thereby improving user experience.

[0116] In various embodiments of the present application, carrier, CC and cell are all concepts used to describe frequency domain resources. In the absence of logical conflicts, the three can be equivalently replaced.

[0117] 5. Cell switching.

[0118] A cell can be regarded as providing a wireless signal coverage area identified by a PCI or CGI. The coverage area of ​​each base station can be divided into one or more cells. In an embodiment of the present application, different cells may correspond to different base stations. For example, the base station corresponding to cell 1 and the base station corresponding to cell 2 may be different base stations, that is, cell 1 and cell 2 may be managed by different base stations. The base station corresponding to cell 1 and the base station corresponding to cell 2 may also be the same base station, that is, cell 1 and cell 2 may be managed by the same base station. This situation may be referred to as co-stationing of cell 1 and cell 2. Optionally, when cell 1 and cell 2 are co-stationed, cell 1 and cell 2 have the same baseband processing unit and intermediate frequency processing unit, but have different radio frequency processing units.

[0119] Cells serving a terminal can be divided into PCells and SCells. Therefore, both PCells and SCells can be referred to as serving cells for the terminal. In a Carrier Access Control (CA) scenario, a base station can configure a PCell and one or more SCells for the terminal. The PCell is the cell in which the terminal maintains an RRC connection with the base station, while the remaining serving cells for the terminal are referred to as SCells. SCells can be flexibly activated / deactivated using DCI or MAC control elements (CEs). After an RRC connection is established, the base station can configure an SCell for the terminal to provide additional radio resources.

[0120] The above description of the cell is an example rather than a limitation. With the development of technology, concepts with the same or similar functions as the cell may emerge, and these concepts are also applicable to the embodiments of the present application.

[0121] Due to changes in the terminal's mobility or channel state, the cell to which the terminal is connected may change, that is, the terminal may switch from one cell to another, wherein the cell before the switch may be referred to as the source cell or anchor cell, and the cell after the switch may be referred to as the target cell. As an optional example, cell switching may be interpreted as the terminal transmitting on the target cell indicated by the handover signaling and ceasing transmission on the source cell, or cell switching may be interpreted as a change in the transmitting cell.

[0122] Figure 4 is a schematic diagram of a cell switching scenario. In Figure 4, the terminal currently uses two carriers (CC1 and CC2) for communication, where the cell corresponding to CC1 is the PCell and the cell corresponding to CC2 is the SCell. The terminal also supports communication using CC3 and CC4, but CC3 and CC4 are not activated. The cells corresponding to CC3 and CC4 are non-serving cells. As the terminal moves, the channel status of CC1 and CC2 deteriorates. The terminal can use CC3 and CC4 for communication instead of CC1 and CC2. For example, the terminal switches from the cell corresponding to CC1 to the cell corresponding to CC3, and from the cell corresponding to CC2 to the cell corresponding to CC4. The cells corresponding to CC1 and CC2 are the cells before the switch and can be called source cells. The cells corresponding to CC3 and CC4 are the cells after the switch and can be called target cells. After the cell handover is completed, the cell corresponding to CC3 becomes the PCell, the cell corresponding to CC4 becomes the SCell, and the cells corresponding to CC1 and CC2 become non-serving cells. The process from CC1 to CC3 can be called PCell handover, the process from CC2 to CC4 can be called SCell handover, or the process from CC2 to CC4 can be called SCell activation.

[0123] It should be understood that cell switching may be switching from a cell of one base station to a cell of another base station, or switching between different cells of the same base station. In addition, cell switching may be triggered by the base station, the terminal, or a third-party device other than the base station or the terminal.

[0124] In the scenario shown in FIG4 , the base station can use MAC CE to trigger PCell switching. After the PCell switching is completed, the SCell activation can be completed through cell activation. The process of PCell switching and SCell activation is shown in FIG5 .

[0125] In Figure 5, the terminal can complete downlink and uplink synchronization with the target PCell before receiving the MAC CE instructing PCell switching. After receiving the MAC CE instructing PCell switching, the terminal performs PCell switching. The PCell switching process includes steps such as MAC CE processing, L2 / L3 reconfiguration, baseband retuning, and RF retuning. After the PCell switching is completed, the base station sends signaling (such as MAC CE) instructing the terminal to activate the SCell. The terminal performs SCell activation based on the signaling. The SCell activation process includes steps such as MAC CE parsing, hybrid automatic repeat request (HARQ) processing, SSB or TRS-based activation, and channel state information (CSI) reporting.

[0126] In the handover process shown in FIG5 , it takes approximately 20 to 55 ms from the start of PCell handover to the completion of target SCell activation. This is a relatively long time. During this time, the terminal cannot use carrier aggregation for communication, which has a negative impact on user experience.

[0127] The following describes a method for switching cells provided by an embodiment of the present application with reference to the accompanying drawings.

[0128] FIG6 is a schematic flow chart of a method for switching cells provided by an embodiment of the present application. As shown in FIG6, the serving cell of the terminal in method 600 includes a first primary cell and a first secondary cell, and the method 600 includes:

[0129] S610: The terminal receives first information, where the first information instructs the terminal to switch a primary cell from a first primary cell to a second primary cell, and the first information includes an identifier of the second secondary cell.

[0130] Accordingly, the base station generates and sends first information.

[0131] In various embodiments of the present application, "the first information instructs the terminal to switch the primary cell from the first primary cell to the second primary cell" can also be expressed as: the first information instructs the terminal to transmit RRC signaling on the second primary cell; or it can also be expressed as: the first information instructs the terminal to switch the RRC connection between the terminal and the base station from the first primary cell to the second primary cell. Accordingly, for the terminal or the base station, "switching the primary cell from the first primary cell to the second primary cell" can be expressed as: transmitting RRC signaling on the second primary cell; or, "switching the primary cell from the first primary cell to the second primary cell" can be expressed as: transmitting RRC signaling on the second primary cell, and stopping transmitting RRC signaling on the first primary cell; or, "switching the primary cell from the first primary cell to the second primary cell" can be expressed as: transmitting RRC signaling on the second primary cell, wherein the first primary cell is the primary service cell before receiving (or sending) the first information, and the second primary cell is the primary service cell after receiving (or sending) the first information. "Switching the secondary cell from the first secondary cell to the second secondary cell" can be expressed as: performing data transmission on the second secondary cell; or, "switching the secondary cell from the first secondary cell to the second secondary cell" can be expressed as: performing data transmission on the second secondary cell, and stopping data transmission on the first secondary cell; or, "switching the secondary cell from the first secondary cell to the second secondary cell" can be expressed as: performing data transmission on the second secondary cell, wherein, before receiving (or sending) the first information, the first secondary cell is the service cell and the second secondary cell is the non-service cell, and after receiving (or sending) the first information, the first secondary cell is the non-service cell and the second secondary cell is the service cell.

[0132] In various embodiments of the present application, "the first information instructs the terminal to switch the primary cell from the first primary cell to the second primary cell" can also be expressed as: the first information instructs the terminal to change the primary cell to the second primary cell. Accordingly, for the terminal or base station, "switching the primary cell from the first primary cell to the second primary cell" can be expressed as: changing the primary cell to the second primary cell; and "switching the secondary cell from the first secondary cell to the second secondary cell" can be expressed as: changing the secondary cell to the second secondary cell. "Change" can be interpreted as "switch."

[0133] The first information is information generated and sent by the base station corresponding to the first primary cell (ie, source PCell). The first information may be an RRC message, a MAC CE, or a DCI, or a field in the RRC message, MAC CE, or DCI.

[0134] The first information can be indicated in an explicit manner or in an implicit manner. When an explicit manner is used, the first information may include a dedicated field, such as a first field. When the value of the first field is "1", the first field, combined with the identifier of the second primary cell, indicates that the terminal switches from the first primary cell to the second primary cell, wherein the identifier of the second primary cell can be sent to the terminal alone or together with the first field; when the value of the first field is "0", it indicates that the terminal does not switch the primary cell. When an implicit manner is used, the first information may reuse some fields for indication. For example, the MAC CE may include the identifier of the second primary cell, and the identifier of the second primary cell indicates the target PCell. The first information may reuse the identifier of the second primary cell. When the terminal receives the identifier of the second primary cell, the terminal determines to perform the primary cell switch, and determines that the target PCell is the second primary cell.

[0135] The embodiments of the present application do not limit the specific form of the first information and the method of sending the first information.

[0136] The identifier of the second secondary cell may be a PCI, a CGI or a serving cell index, or other information used to identify the second secondary cell. The embodiments of the present application do not limit the specific form of the identifier of the second secondary cell.

[0137] The first information including the identifier of the second secondary cell also instructs the terminal to switch from the first secondary cell to the second secondary cell, wherein the first information can be indicated in an explicit manner or in an implicit manner. When the explicit manner is adopted, the first information may include a dedicated field, such as the second field. When the value of the second field is "1", the second field, combined with the identifier of the second secondary cell, instructs the terminal to switch from the first secondary cell to the second secondary cell, wherein the identifier of the second secondary cell can be sent to the terminal alone or together with the second field; when the value of the second field is "0", it instructs the terminal not to perform secondary cell switching. When the implicit manner is adopted, the first information may reuse some fields for indication. For example, the identifier of the second secondary cell indicates the target SCell. The first information may reuse the identifier of the second secondary cell. When the terminal receives the identifier of the second secondary cell, the terminal determines to perform secondary cell switching, and determines that the target SCell is the second secondary cell.

[0138] Before sending the first information, the base station may configure a candidate cell set, which includes at least one candidate primary cell and / or at least one candidate secondary cell. Alternatively, the base station may configure two candidate cell sets, wherein one candidate cell set includes at least one candidate primary cell and the other candidate cell set includes at least one candidate secondary cell. Taking the previous case as an example, the base station may configure a candidate cell set including four cells for the terminal through an RRC message, and the four cells are cell 1, cell 2, cell 3 and cell 4. If the identifier of the second secondary cell carried by the first information is the identifier of cell 4, the terminal may determine that the second secondary cell is cell 4; optionally, if the first information also carries the identifier of the second primary cell, and the identifier of the second primary cell is the identifier of cell 3, the terminal may determine that the second primary cell is cell 3. By pre-configuring the candidate cell set, the base station may configure some parameters of the target cell to the terminal in advance, thereby reducing the delay of cell switching.

[0139] After receiving the first information, the terminal may perform the following steps.

[0140] S620: Switch the primary cell from the first primary cell to the second primary cell according to the first information, and switch the secondary cell from the first secondary cell to the second secondary cell.

[0141] Before the terminal switches to the second secondary cell, it needs to perform operations such as downlink synchronization and channel state measurement. The terminal can complete downlink synchronization with the second primary cell before receiving the first information. Therefore, the terminal can determine the measurement configuration of the second secondary cell, such as SMTC, through the downlink synchronization information of the second primary cell, and then receive the downlink synchronization signal (such as SSB) of the second secondary cell based on the measurement configuration of the second secondary cell, and perform downlink synchronization and other operations according to the downlink synchronization signal. The downlink synchronization can be performed by performing a cell search to obtain the time and frequency synchronization of the second secondary cell.

[0142] During the cell switching process, the C-RNTI assigned to the terminal by the base station needs to be updated. For example, during the switching process from the first secondary cell to the second secondary cell, the C-RNTI of the terminal needs to be updated from the first C-RNTI (the C-RNTI assigned to the terminal by the first secondary cell) to the second C-RNTI (the C-RNTI assigned to the terminal by the second secondary cell). One implementation method is: each candidate cell is assigned a C-RNTI to the terminal, and the first primary cell can send the C-RNTIs assigned to the terminal by all candidate cells to the terminal through an RRC message before sending the first information; another implementation method is: the first information carries the C-RNTI assigned to the terminal by the target cell (such as the second primary cell and the second secondary cell). Since the number of C-RNTIs carried by the first information is less than the number of C-RNTIs carried by the RRC message, the latter implementation method reduces the signaling overhead caused by updating the C-RNTI compared to the former implementation method.

[0143] After the terminal obtains the measurement configuration of the second secondary cell and the C-RNTI assigned to the terminal by the second secondary cell, it can perform a handover operation to the second secondary cell. Thus, in method 600, the handover of the secondary cell can be performed synchronously with the handover of the primary cell. Compared with the method of waiting for the completion of the handover of the primary cell before activating the secondary cell, method 600 can reduce the delay of the secondary cell handover.

[0144] Secondary cell switching includes operations such as downlink synchronization and channel state measurement, wherein downlink synchronization and channel state measurement can be performed before receiving the first information or after receiving the first information. Different situations are described in detail below. It should be noted that the various operations (such as synchronization, channel measurement, etc.) mentioned in the various embodiments of this application and the execution order of each operation are examples rather than limitations. Primary cell switching and secondary cell switching may also include other operations. The embodiments of this application do not limit the specific operations in the primary cell switching and secondary cell switching process.

[0145] Case 1: Downlink synchronization and channel state measurement are performed after receiving the first information.

[0146] Optionally, in method 600, the process of primary cell switching and secondary cell switching is shown in Figure 7. In Figure 7, the terminal can complete downlink synchronization and uplink synchronization with the second primary cell (i.e., target PCell) before receiving the MAC CE indicating the primary cell switching (an example of the first information). After receiving the MAC CE indicating the primary cell switching, the terminal performs the primary cell switching. For example, the base station can pre-configure the candidate primary cells, and the terminal performs downlink synchronization and uplink synchronization with each candidate primary cell; the MAC CE carries the identifier of the second primary cell, and the second primary cell belongs to the pre-configured candidate primary cell. After receiving the MAC CE, the terminal can directly perform steps such as MAC CE parsing, L2 / L3 reconfiguration, baseband retuning and RF retuning, without having to perform downlink synchronization and uplink synchronization with the second primary cell.

[0147] After receiving the MAC CE indicating the primary cell handover, the terminal can receive the SSB, periodic TRS (P-TRS) or A-TRS of the second secondary cell (i.e., the target SCell) to perform AGC and downlink synchronization. During the downlink synchronization process, the terminal can first perform coarse synchronization and then fine synchronization.

[0148] After downlink synchronization is completed, the terminal can receive the reference signal of the second secondary cell, perform channel state measurement based on the reference signal, generate channel state information and send the channel state information to the first primary cell, wherein the reference signal is, for example, CSI-RS, and the channel state information is, for example, CSI.

[0149] The above-mentioned channel state measurement can be semi-continuous measurement, that is, the base station configures periodic CSI-RS resources in advance, and the MAC CE indicating the primary cell handover triggers the periodic CSI-RS resources to take effect. When the terminal receives the MAC CE, it starts to receive CSI-RS on the periodic CSI-RS resources to perform channel state measurement and reporting.

[0150] The above-mentioned channel state measurement can also be aperiodic measurement, that is, the base station configures aperiodic CSI-RS resources in advance, and the MAC CE indicating the primary cell switching carries an indication of triggering aperiodic CSI measurement. When the terminal receives the MAC CE, it starts to receive CSI-RS on the aperiodic CSI-RS resources, performs channel state measurement and reporting, so that the base station can obtain channel state information earlier.

[0151] After receiving the channel state information, the base station considers that the secondary cell handover is completed.

[0152] Based on the process shown in Figure 7, the start time of the secondary cell handover delay can be defined as the time when the terminal receives the MAC CE indicating the primary cell handover, and the end time of the secondary cell handover delay can be defined as the time when the terminal sends the channel state information. The secondary cell handover delay includes: the time it takes for the terminal to parse the MAC CE, the time it takes for the terminal to feedback the MAC CE reception status based on HARQ, the time it takes for the terminal to perform downlink synchronization based on SSB or A-TRS, and the time it takes for the terminal to measure and report the channel state, etc.

[0153] Case 2: Downlink synchronization is performed before receiving the first information, and channel state measurement is performed after receiving the first information.

[0154] Optionally, in method 600, the process of primary cell switching and secondary cell switching is shown in Figure 8. In Figure 8, the terminal can complete downlink synchronization and uplink synchronization with the second primary cell (i.e., the target PCell) before receiving the MAC CE indicating the primary cell switching. After receiving the MAC CE indicating the primary cell switching, the terminal performs the primary cell switching. For example, the base station can pre-configure the candidate primary cells, and the terminal performs downlink synchronization and uplink synchronization with each candidate primary cell; the MAC CE carries the identifier of the second primary cell, and the second primary cell belongs to the pre-configured candidate primary cell. After receiving the MAC CE, the terminal can directly perform steps such as MAC CE parsing, L2 / L3 reconfiguration, baseband retuning and RF retuning, without having to perform downlink synchronization and uplink synchronization with the second primary cell.

[0155] The terminal can complete the downlink synchronization with the second secondary cell (i.e., the target SCell) before receiving the MAC CE indicating the switching of the primary cell. For example, the base station can pre-configure the candidate secondary cells, and the terminal performs downlink synchronization with each candidate secondary cell; the MAC CE carries the identifier of the second secondary cell, and the second secondary cell belongs to the pre-configured candidate primary cell. After receiving the MAC CE, the terminal can directly perform steps such as MAC CE parsing and channel state measurement, without having to perform downlink synchronization with the second secondary cell, thereby reducing the delay of the secondary cell switching.

[0156] Optionally, before receiving the MAC CE indicating the primary cell handover, the terminal may receive the SSB of the second secondary cell and perform downlink coarse synchronization according to the SSB. After the downlink coarse synchronization is completed, the terminal may receive the SSB, P-TRS, or A-TRS of the second secondary cell and perform downlink fine synchronization and other operations.

[0157] After receiving the MAC CE indicating the switching of the primary cell, the terminal can receive the reference signal of the second secondary cell, perform channel state measurement based on the reference signal, generate channel state information and send the channel state information to the first primary cell, where the reference signal is, for example, CSI-RS and the channel state information is, for example, CSI.

[0158] The above-mentioned channel state measurement can be semi-continuous measurement, that is, the base station configures periodic CSI-RS resources in advance, and the MAC CE indicating the primary cell handover triggers the periodic CSI-RS resources to take effect. When the terminal receives the MAC CE, it starts to receive CSI-RS on the periodic CSI-RS resources to perform channel state measurement and reporting.

[0159] The above-mentioned channel state measurement can also be aperiodic measurement, that is, the base station configures aperiodic CSI-RS resources in advance, and the MAC CE indicating the primary cell switching carries an indication of triggering aperiodic CSI measurement. When the terminal receives the MAC CE, it starts to receive CSI-RS on the aperiodic CSI-RS resources, performs channel state measurement and reporting, so that the base station can obtain channel state information earlier.

[0160] After receiving the channel state information, the base station considers that the secondary cell handover is completed.

[0161] Based on the process shown in Figure 8, the starting time of the secondary cell handover delay can be defined as the moment when the terminal receives the MAC CE indicating the primary cell handover, and the ending time of the secondary cell handover delay can be defined as the moment when the terminal sends the channel state information. The secondary cell handover delay includes: the time it takes for the terminal to parse the MAC CE, the time it takes for the terminal to provide HARQ-based feedback on the MAC CE reception status, and the time it takes for the terminal to measure and report the channel state. In Figure 8, the secondary cell handover delay may be greater than the primary cell handover delay, less than the primary cell handover delay, or even equal to the primary cell handover delay.

[0162] Case 3: Downlink synchronization and channel state measurement are performed before receiving the first information.

[0163] Optionally, in method 600, the process of primary cell switching and secondary cell switching is shown in Figure 9. In Figure 9, the terminal can complete downlink synchronization and uplink synchronization with the second primary cell (i.e., the target PCell) before receiving the MAC CE indicating the primary cell switching. After receiving the MAC CE indicating the primary cell switching, the terminal performs the primary cell switching. For example, the base station can pre-configure the candidate primary cells, and the terminal performs downlink synchronization and uplink synchronization with each candidate primary cell; the MAC CE carries the identifier of the second primary cell, and the second primary cell belongs to the pre-configured candidate primary cell. After receiving the MAC CE, the terminal can directly perform steps such as MAC CE parsing, L2 / L3 reconfiguration, baseband retuning and RF retuning, without having to perform downlink synchronization and uplink synchronization with the second primary cell.

[0164] The terminal can complete the downlink synchronization with the second secondary cell (i.e., the target SCell) before receiving the MAC CE indicating the switching of the primary cell. For example, the base station can pre-configure the candidate secondary cells, and the terminal performs downlink synchronization with each candidate secondary cell; the MAC CE carries the identifier of the second secondary cell, and the second secondary cell belongs to the pre-configured candidate primary cell. After receiving the MAC CE, the terminal can directly perform steps such as MAC CE parsing, without having to perform downlink synchronization and channel state measurement with the second secondary cell, thereby reducing the delay of the secondary cell switching.

[0165] Optionally, before receiving the MAC CE indicating the primary cell handover, the terminal may receive the SSB of the second secondary cell and perform downlink coarse synchronization according to the SSB. After the downlink coarse synchronization is completed, the terminal may receive the SSB, P-TRS, or A-TRS of the second secondary cell and perform downlink fine synchronization and other operations.

[0166] Before receiving the MAC CE indicating the switching of the primary cell and after the downlink fine synchronization is completed, the terminal can receive the reference signal of the second secondary cell, perform channel state measurement based on the reference signal, generate channel state information and send the channel state information to the first primary cell, where the reference signal is, for example, CSI-RS and the channel state information is, for example, CSI.

[0167] The above-mentioned channel state measurement can be semi-continuous measurement, that is, the base station configures periodic CSI-RS resources in advance, and the MAC CE indicating the primary cell handover triggers the periodic CSI-RS resources to take effect. When the terminal receives the MAC CE, it starts to receive CSI-RS on the periodic CSI-RS resources to perform channel state measurement and reporting.

[0168] The above-mentioned channel state measurement can also be aperiodic measurement, that is, the base station configures aperiodic CSI-RS resources in advance, and the MAC CE indicating the primary cell switching carries an indication of triggering aperiodic CSI measurement. When the terminal receives the MAC CE, it starts to receive CSI-RS on the aperiodic CSI-RS resources, performs channel state measurement and reporting, so that the base station can obtain channel state information earlier.

[0169] After receiving the channel state information, the base station considers that the secondary cell handover is completed.

[0170] Based on the process shown in Figure 9, the start time of the secondary cell handover delay can be defined as the moment when the terminal receives the MAC CE indicating the primary cell handover, and the end time of the secondary cell handover delay can be defined as the moment when the terminal sends the channel state information. The secondary cell handover delay includes the time it takes for the terminal to parse the MAC CE and the time it takes for the terminal to provide HARQ-based feedback on the MAC CE reception status. In Figure 9, the secondary cell handover delay may be greater than the primary cell handover delay, less than the primary cell handover delay, or even equal to the primary cell handover delay.

[0171] Optionally, in method 600, before receiving the first information, the terminal may further perform the following steps:

[0172] Second information is sent, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

[0173] Performing both primary and secondary cell handovers simultaneously requires the terminal's capability support, and some terminals may not have this capability. Therefore, the terminal reports in advance that it has the capability to perform both primary and secondary cell handovers simultaneously, and then performs secondary cell handover based on the first information, to avoid secondary cell handover failures due to lack of this capability. For example, if the terminal does not have the capability to perform both primary and secondary cell handovers simultaneously, and the terminal does not report the second information, the base station may assume that the terminal has the capability to perform both primary and secondary cell handovers simultaneously. After sending the primary cell handover signaling, the base station will no longer send the secondary cell activation signaling, and the terminal will be unable to complete the activation of the secondary cell and will therefore be unable to communicate in the target secondary cell.

[0174] The second information can be indicated in an explicit manner or in an implicit manner. When the explicit manner is adopted, the second information may include a dedicated field, such as the third field. When the value of the third field is "1", it indicates that the terminal supports simultaneous switching of the primary cell and the secondary cell. When the value of the third field is "0", it indicates that the terminal does not support simultaneous switching of the primary cell and the secondary cell. When the implicit manner is adopted, the second information may reuse some fields for indication. The second information may reuse some information formats or information types for indication. For example, when the format of a certain information sent by the terminal to the base station is format A, it indicates that the terminal supports simultaneous switching of the primary cell and the secondary cell. When the format of a certain information sent by the terminal to the base station is format B, it indicates that the terminal does not support simultaneous switching of the primary cell and the secondary cell.

[0175] The embodiments of the present application do not limit the specific form of the second information and the method for sending the second information.

[0176] After the terminal sends the second information, the base station can process it according to the content indicated by the second information. For example, when the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching, the base station can configure the resources required for the secondary cell switching for the terminal before sending the first information, such as the downlink synchronization resources and / or channel state measurement resources of the secondary cell.

[0177] Optionally, the terminal may further report whether it supports early downlink synchronization of the secondary cell and / or measurement of the secondary cell channel state. If the terminal supports early downlink synchronization of the secondary cell (or, the terminal supports downlink synchronization of the secondary cell before receiving the first information, or, the terminal supports downlink synchronization of the secondary cell when the secondary cell is in a deactivated state), the base station may configure the resources required for downlink synchronization of the secondary cell (such as SSB configuration parameters) for the terminal before sending the first information; if the terminal supports early channel state measurement (or, the terminal supports secondary cell channel state measurement before receiving the first information, or, the terminal supports secondary cell channel state measurement when the secondary cell is in a deactivated state), the base station may configure the resources required for secondary cell channel state measurement (such as CSI-RS configuration parameters) for the terminal before sending the first information.

[0178] The above description is made by taking the switching of two secondary cells as an example, but the application scenario of the method 600 is not limited thereto. The method 600 can also be applied to the switching scenario of more secondary cells.

[0179] For example, the service cell of the terminal also includes a third secondary cell, and the first information may also include an identifier of the fourth secondary cell. After receiving the first information, the terminal determines to switch from the first secondary cell and the third secondary cell to the second secondary cell and the fourth secondary cell. The switching of multiple secondary cells can be performed simultaneously or separately, that is, the terminal can simultaneously execute the operation of switching from the first secondary cell to the second secondary cell and the operation of switching from the third secondary cell to the fourth secondary cell; or, the terminal can first execute the operation of switching from the first secondary cell to the second secondary cell, and then execute the operation of switching from the third secondary cell to the fourth secondary cell; or, the terminal can first execute the operation of switching from the third secondary cell to the fourth secondary cell, and then execute the operation of switching from the first secondary cell to the second secondary cell.

[0180] Optionally, the first information further includes an identifier of a second primary cell, and the identifier of the second primary cell is the same as the identifier of the first primary cell.

[0181] When the identifier of the second primary cell is the same as the identifier of the first primary cell, the terminal may understand that there is no need to perform primary cell switching, and only performs secondary cell switching.

[0182] As shown in Figure 10, a terminal currently uses two carriers (CC1 and CC2) for communication. The cell corresponding to CC1 is the PCell, and the cell corresponding to CC2 is the SCell. The terminal also supports communication using CC3 and CC4, but CC3 and CC4 are not activated. The cells corresponding to CC3 and CC4 are non-serving cells. As the terminal moves, the channel state of CC2 deteriorates. The terminal can use CC1 and CC4 for communication, and no longer uses CC1 and CC2. For example, the base station sends first information to the terminal. The first information includes the identifier of a second primary cell and the identifier of a second secondary cell. The identifier of the second secondary cell is the cell identifier corresponding to CC4, and the identifier of the second primary cell is the cell identifier corresponding to CC1 (i.e., the identifier of the current source PCell). After receiving the first information, the terminal obtains the identifier of the second primary cell from the first information. If the identifier of the second primary cell is the same as the cell identifier corresponding to CC1, it determines not to perform a primary cell handover and only performs a secondary cell handover. After the cell handover is completed, the PCell remains the cell corresponding to CC1, and the SCell becomes the cell corresponding to CC4. In this way, the function of switching the secondary cell independently can be achieved without changing the existing primary cell switching process, which has better forward compatibility.

[0183] FIG11 is another method for switching cells provided by an embodiment of the present application. The method 1100 includes:

[0184] S1110 : The terminal receives third information, where the third information instructs the terminal to switch a secondary cell from a first secondary cell to a second secondary cell.

[0185] Accordingly, the base station generates and sends third information.

[0186] In various embodiments of the present application, "the third information instructs the terminal to switch the secondary cell from the first secondary cell to the second secondary cell" can also be expressed as: the third information instructs the terminal to transmit on the second secondary cell. Accordingly, for the terminal or base station, "switching the secondary cell from the first secondary cell to the second secondary cell" can be expressed as: transmitting on the second secondary cell.

[0187] In various embodiments of the present application, "the third information instructs the terminal to switch the secondary cell from the first secondary cell to the second secondary cell" can also be expressed as: the third information instructs the terminal to change the secondary cell to the second secondary cell. Accordingly, for the terminal or base station, "switching the secondary cell from the first secondary cell to the second secondary cell" can be expressed as: changing the secondary cell to the second secondary cell. Here, "change" can be interpreted as "switching."

[0188] The third information may be information generated and sent by the base station corresponding to the primary cell, an RRC message, a MAC CE, or a DCI, or a field in the RRC message, MAC CE, or DCI.

[0189] The third information can be indicated in an explicit manner or in an implicit manner. When the explicit manner is adopted, the third information may include a dedicated field, such as the fourth field. When the value of the fourth field is "1", the fourth field, combined with the identifier of the second secondary cell, indicates that the terminal switches from the first secondary cell to the second secondary cell, wherein the identifier of the second secondary cell can be sent to the terminal alone or together with the second field; when the value of the fourth field is "0", it indicates that the terminal does not switch the secondary cell. When the implicit manner is adopted, the third information may reuse some fields for indication. For example, the MAC CE may include the identifier of the second secondary cell, and the identifier of the second secondary cell indicates the target SCell. The third information may reuse the identifier of the second secondary cell. When the terminal receives the identifier of the second secondary cell, the terminal determines to perform the secondary cell switch, and determines that the target SCell is the second secondary cell.

[0190] The embodiments of the present application do not limit the specific form of the third information and the method of sending the third information.

[0191] Before sending the third information, the base station may configure a candidate cell set, which includes at least one candidate primary cell and / or at least one candidate secondary cell. Alternatively, the base station may configure two candidate cell sets, wherein one candidate cell set includes at least one candidate primary cell and the other candidate cell set includes at least one candidate secondary cell. Taking the latter case as an example, the base station may configure a candidate secondary cell set including four cells for the terminal through an RRC message, where the four cells are cell 1, cell 2, cell 3, and cell 4. If the identifier of the second secondary cell carried by the third information is the identifier of cell 4, the terminal may determine that the second secondary cell is cell 4. By pre-configuring the candidate secondary cell set, the base station may configure some parameters of the target secondary cell to the terminal in advance, thereby reducing the delay of the secondary cell switching.

[0192] After receiving the third information, the terminal may perform the following steps.

[0193] S1120: Switch the secondary cell from the first secondary cell to the second secondary cell according to the third information.

[0194] Before the terminal switches to the second secondary cell, it needs to perform operations such as downlink synchronization and channel state measurement. The terminal may obtain the measurement configuration of the second secondary cell, such as SMTC, from the primary cell before receiving the third information, and then receive the downlink synchronization signal (e.g., SSB) of the second secondary cell based on the measurement configuration of the second secondary cell, and perform downlink synchronization and other operations according to the downlink synchronization signal. The downlink synchronization may include performing a cell search to obtain time and frequency synchronization of the second secondary cell.

[0195] During the cell switching process, the C-RNTI assigned to the terminal by the base station needs to be updated. For example, during the switching process from the first secondary cell to the second secondary cell, the C-RNTI of the terminal needs to be updated from the first C-RNTI (the C-RNTI assigned to the terminal by the first secondary cell) to the second C-RNTI (the C-RNTI assigned to the terminal by the second secondary cell). One implementation method is: each candidate secondary cell is assigned a C-RNTI to the terminal, and the base station can send the C-RNTIs assigned to the terminal by all candidate secondary cells to the terminal through an RRC message before sending the third information; another implementation method is: the third information carries the C-RNTI assigned to the terminal by the target secondary cell. Since the number of C-RNTIs carried by the third information is less than the number of C-RNTIs carried by the RRC message, the latter implementation method reduces the signaling overhead caused by updating the C-RNTI compared to the former implementation method.

[0196] In method 1100, the handover process for the secondary cell is decoupled from the handover process for the primary cell. The terminal performs the handover of the secondary cell according to the third information, without having to pay attention to whether the primary cell has been switched. Compared to the method of waiting for the primary cell handover to complete before activating the secondary cell, method 1100 can reduce the delay in the handover of the secondary cell. The changes in the cell before and after the terminal executes method 1100 can be seen in Figure 10.

[0197] It should be noted that some concepts in method 1100 are the same as those in method 600, and the meanings of these same concepts are the same. For example, the identifier of the second secondary cell in method 1100 is the same as the identifier of the second secondary cell in method 600, and the meaning of the identifier of the second secondary cell in method 1100 can be the same as the meaning of the identifier of the second secondary cell in method 600. Hereinafter, the meanings of concepts such as "reference signal of the second secondary cell" and "channel state measurement" can also be the same as the meanings of the corresponding concepts in method 600, and the meanings of these same concepts are not repeated here.

[0198] Secondary cell switching includes operations such as downlink synchronization and channel state measurement, where downlink synchronization and channel state measurement can be performed before or after receiving the third information. Different situations are described in detail below. It should be noted that the various operations (such as synchronization, channel measurement, etc.) and the execution order of each operation mentioned in the various embodiments of this application are examples rather than limitations. Secondary cell switching may also include other operations. The embodiments of this application do not limit the specific operations in the secondary cell switching process.

[0199] Case 4: Downlink synchronization and channel state measurement are performed after receiving the third information.

[0200] Optionally, in method 1100, the secondary cell handover process is shown in FIG12. In FIG12, after receiving the MAC CE (an example of the third information) indicating the secondary cell handover, the terminal may receive the SSB, P-TRS, or A-TRS of the second secondary cell (i.e., the target SCell) and perform operations such as AGC and downlink synchronization. During the downlink synchronization process, the terminal may first perform coarse synchronization and then fine synchronization.

[0201] After downlink synchronization is completed, the terminal can receive the reference signal of the second secondary cell, perform channel state measurement based on the reference signal, generate channel state information and send the channel state information to the primary cell, wherein the reference signal is, for example, CSI-RS and the channel state information is, for example, CSI.

[0202] After receiving the channel state information, the base station considers that the secondary cell handover is completed.

[0203] Based on the process shown in Figure 12, the start time of the secondary cell handover delay can be defined as the time when the terminal receives the MAC CE indicating the secondary cell handover, and the end time of the secondary cell handover delay can be defined as the time when the terminal sends the channel state information. The secondary cell handover delay includes: the time it takes for the terminal to parse the MAC CE, the time it takes for the terminal to provide HARQ feedback on the MAC CE reception status, the time it takes for the terminal to perform downlink synchronization based on the SSB or A-TRS, and the time it takes for the terminal to measure and report the channel state, etc.

[0204] Case 5: Downlink synchronization is performed before receiving the third information, and channel state measurement is performed after receiving the third information.

[0205] Optionally, in method 1100, the secondary cell handover process is shown in FIG13. In FIG13, the terminal may complete downlink synchronization with the second secondary cell (i.e., the target SCell) before receiving a MAC CE indicating secondary cell handover. For example, the base station may pre-configure candidate secondary cells, and the terminal performs downlink synchronization with each candidate secondary cell. The MAC CE carries an identifier of the second secondary cell, and the second secondary cell is a pre-configured candidate secondary cell. After receiving the MAC CE, the terminal may directly perform steps such as MAC CE parsing and channel state measurement without further performing downlink synchronization with the second secondary cell, thereby reducing the delay of the secondary cell handover.

[0206] Optionally, before receiving the MAC CE indicating the secondary cell handover, the terminal may receive the SSB of the second secondary cell and perform downlink coarse synchronization based on the SSB. After the downlink coarse synchronization is completed, the terminal may receive the SSB, P-TRS, or A-TRS of the second secondary cell and perform downlink fine synchronization and other operations.

[0207] After receiving the MAC CE indicating the switching of the secondary cell, the terminal can receive the reference signal of the second secondary cell, perform channel state measurement based on the reference signal, generate channel state information and send the channel state information to the primary cell, where the reference signal is, for example, CSI-RS and the channel state information is, for example, CSI.

[0208] After receiving the channel state information, the base station considers that the secondary cell handover is completed.

[0209] Based on the process shown in Figure 13, the start time of the secondary cell handover delay can be defined as the time when the terminal receives the MAC CE indicating the secondary cell handover, and the end time of the secondary cell handover delay can be defined as the time when the terminal sends the channel state information. The secondary cell handover delay includes: the time it takes for the terminal to parse the MAC CE, the time it takes for the terminal to provide HARQ feedback on the MAC CE reception status, and the time it takes for the terminal to measure and report the channel state.

[0210] Case 6: Downlink synchronization and channel state measurement are performed before receiving the third information.

[0211] Optionally, in method 1100, the secondary cell handover process is shown in FIG14. In FIG14, the terminal may complete downlink synchronization with the second secondary cell (i.e., the target SCell) before receiving a MAC CE indicating secondary cell handover. For example, the base station may pre-configure candidate secondary cells, and the terminal performs downlink synchronization with each candidate secondary cell. The MAC CE carries an identifier of the second secondary cell, and the second secondary cell is a pre-configured candidate secondary cell. After receiving the MAC CE, the terminal may directly perform steps such as MAC CE parsing, without having to perform downlink synchronization and channel state measurement with the second secondary cell, thereby reducing the delay of the secondary cell handover.

[0212] Optionally, before receiving the MAC CE indicating the secondary cell handover, the terminal may receive the SSB of the second secondary cell and perform downlink coarse synchronization based on the SSB. After the downlink coarse synchronization is completed, the terminal may receive the SSB, P-TRS, or A-TRS of the second secondary cell and perform downlink fine synchronization and other operations.

[0213] Before receiving the MAC CE indicating the switching of the secondary cell and after the downlink fine synchronization is completed, the terminal can receive the reference signal of the second secondary cell, perform channel state measurement based on the reference signal, generate channel state information and send the channel state information to the primary cell, where the reference signal is, for example, CSI-RS and the channel state information is, for example, CSI.

[0214] After receiving the channel state information, the base station considers that the secondary cell handover is completed.

[0215] Based on the process shown in Figure 14, the start time of the secondary cell handover delay can be defined as the moment when the terminal receives the MAC CE indicating the secondary cell handover, and the end time of the secondary cell handover delay can be defined as the moment when the terminal sends the channel state information. The secondary cell handover delay includes the time it takes for the terminal to parse the MAC CE and the time it takes for the terminal to provide HARQ feedback on the MAC CE reception status.

[0216] The above describes in detail the method examples provided by the embodiments of the present application. It is understandable that the corresponding device includes hardware structures and / or software modules corresponding to the execution of each function in order to realize the above functions. Those skilled in the art should easily appreciate that, in combination with the units and algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in a hardware or computer software driven hardware manner depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0217] Figures 15 and 16 are schematic diagrams of the structures of two possible communication devices provided in the embodiments of the present application. These communication devices can be used to implement the functions of the terminal or base station in the above method embodiments, and therefore also have the beneficial effects of the above method embodiments. In the embodiments of the present application, these communication devices can be the terminal shown in Figure 1, the base station described in Figure 1, or a module (such as a chip) applied to the terminal or base station.

[0218] As shown in Figure 15, the communication device 1500 includes a processing unit 1510 and a transceiver unit 1520. Under the control of the processing unit 1510, the transceiver unit 1520 performs the receiving step and / or the sending step. When performing the sending step, the transceiver unit 1520 functions as a sending unit, and when performing the receiving step, the transceiver unit 1520 functions as a receiving unit. The communication device 1500 is used to implement the functions of a terminal or base station in the method embodiments described in Figures 6 or 11 above.

[0219] When the communication device 1500 is used to implement the function of the terminal in the method embodiment described in Figure 6, the transceiver unit 1520 is used to: receive first information, the first information instructs the terminal to switch the primary cell from the first primary cell to the second primary cell, and the first information includes the identifier of the second secondary cell; the processing unit 1510 is used to: switch the primary cell from the first primary cell to the second primary cell according to the first information, and switch the secondary cell from the first secondary cell to the second secondary cell.

[0220] Optionally, before switching from the first secondary cell to the second secondary cell according to the first information, the transceiver unit 1520 is further used to: receive a downlink synchronization signal of the second secondary cell; the processing unit 1510 is further used to: perform a cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

[0221] Optionally, the processing unit 1510 is specifically configured to: before the transceiver unit 1520 receives the first information, perform a cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

[0222] Optionally, before switching from the first secondary cell to the second secondary cell according to the first information, the transceiver unit 1520 is further configured to: receive a reference signal of the second secondary cell; and send channel state information, where the channel state information is determined by the processing unit 1510 based on the reference signal.

[0223] Optionally, the transceiver unit 1520 is specifically configured to: send channel state information before receiving the first information.

[0224] Optionally, before receiving the first information, the transceiver unit 1520 further includes: sending second information, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

[0225] When the communication device 1500 is used to implement the function of the base station in the method embodiment described in Figure 6, the transceiver unit 1520 is used to: send the first information, the first information instructs the terminal to switch the main cell from the first main cell to the second main cell, the first information includes the identifier of the second secondary cell, and the first information also instructs the terminal to switch the secondary cell from the first secondary cell to the second secondary cell, the first main cell and the first secondary cell are the service cells of the terminal; the processing unit 1510 is used to: switch the main cell from the first main cell to the second main cell, and switch the secondary cell from the first secondary cell to the second secondary cell.

[0226] Optionally, the transceiver unit 1520 is further configured to: send a downlink synchronization signal of the second secondary cell.

[0227] Optionally, the transceiver unit 1520 is specifically configured to: send a downlink synchronization signal of the second secondary cell before sending the first information.

[0228] Optionally, the transceiver unit 1520 is further configured to: send a reference signal of the second secondary cell; and receive channel state information, where the channel state information is determined based on the reference signal.

[0229] Optionally, the transceiver unit 1520 is specifically configured to: send a reference signal of the second secondary cell before sending the first information.

[0230] Optionally, before the processing unit 1510 sends the first information, the transceiver unit 1520 is further configured to: receive second information, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

[0231] When the communication device 1500 is used to implement the function of the terminal in the method embodiment described in Figure 11, the transceiver unit 1520 is used to: receive third information, the third information instructing the terminal to switch the secondary cell from the first secondary cell to the second secondary cell; the processing unit 1510 is used to: switch the secondary cell from the first secondary cell to the second secondary cell according to the third information.

[0232] Optionally, before switching the secondary cell from the first secondary cell to the second secondary cell according to the third information, the transceiver unit 1520 is also used to: receive the downlink synchronization signal of the second secondary cell; the processing unit 1510 is also used to: perform cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

[0233] Optionally, the transceiver unit 1520 is specifically configured to: before receiving the third information, receive a downlink synchronization signal of the second secondary cell.

[0234] Optionally, before switching the secondary cell from the first secondary cell to the second secondary cell according to the third information, the transceiver unit 1520 is further used to: receive a reference signal of the second secondary cell; and send channel state measurement information, where the channel state measurement information is determined by the processing unit 1510 based on the reference signal.

[0235] Optionally, the transceiver unit 1520 is specifically configured to: receive a reference signal of the second secondary cell before receiving the third information.

[0236] When the communication device 1500 is used to implement the function of the base station in the method embodiment described in Figure 11, the transceiver unit 1520 is used to: send third information, the third information instructs the terminal to switch the secondary cell from the first secondary cell to the second secondary cell; the processing unit 1510 is used to: switch the secondary cell from the first secondary cell to the second secondary cell.

[0237] Optionally, the transceiver unit 1520 is further configured to: send a downlink synchronization signal of the second secondary cell.

[0238] Optionally, the transceiver unit 1520 is specifically configured to: send a downlink synchronization signal of the second secondary cell before sending the third information.

[0239] Optionally, the transceiver unit 1520 is further configured to: send a reference signal of the second secondary cell; and receive channel state measurement information, where the channel state measurement information is determined based on the reference signal.

[0240] Optionally, the transceiver unit 1520 is specifically configured to: send a reference signal of the second secondary cell before sending the third information.

[0241] Those skilled in the art can clearly understand that when the communication device 1500 is used to implement the functions of a terminal or a base station, the specific working process of the communication device 1500 and the technical effects produced by the execution steps can refer to the description in the corresponding method embodiment mentioned above. For the sake of brevity, they will not be repeated here.

[0242] Communication device 1500 may be a terminal or a base station. Processing unit 1510 may be implemented in hardware or software. When implemented in hardware, processing unit 1510 may be a logic circuit, an integrated circuit, or the like. When implemented in software, processing unit 1510 may be a general-purpose processor implemented by reading software code stored in a storage unit. The storage unit may be integrated into processing unit 1510 or located independently of processing unit 1510.

[0243] As shown in Figure 16, communication device 1600 includes a processor 1610 and an interface circuit 1620. Processor 1610 and interface circuit 1620 are coupled to each other. It will be appreciated that interface circuit 1620 may be a transceiver or an input / output interface. Optionally, communication device 1600 may also include a memory 1630 for storing instructions executed by processor 1610, input data required by processor 1610 to execute instructions, or data generated by processor 1610 after executing instructions.

[0244] When the communication device 1600 is used to implement the method shown in FIG. 6 or FIG. 11 , the processor 1610 is used to implement the functions of the processing unit 1610 , and the interface circuit 1620 is used to implement the functions of the transceiver unit 1620 .

[0245] When the communication device 1600 is a terminal chip (i.e., a chip used in a terminal), the terminal chip implements the functions of the terminal in the above-described method embodiments. When the terminal chip receives information from the base station, it can be understood that the information is first received by other modules in the terminal (such as a radio frequency module or antenna) and then sent to the terminal chip by these modules. When the terminal chip sends information to the base station, it can be understood that the information is first sent to other modules in the terminal (such as a radio frequency module or antenna) and then sent to the base station by these modules.

[0246] When the communication device 1600 is a base station chip (i.e., a chip used in a base station), the base station chip implements the functions of the base station in the above-mentioned method embodiment. When the base station chip receives information from the terminal, it can be understood that the information is first received by other modules in the base station (such as a radio frequency module or antenna) and then sent to the base station chip by these modules. When the base station chip sends information to the terminal, it can be understood that the information is sent to other modules in the base station (such as a radio frequency module or antenna) and then sent to the terminal by these modules.

[0247] In this application, when entity A sends information to entity B, it can be done directly from A to B or indirectly through another entity. Similarly, when entity B receives information from entity A, it can be done directly from entity B or indirectly through another entity. Entities A and B herein can be RAN nodes or terminals, or modules within a RAN node or terminal. The sending and receiving of information can be information exchange between a RAN node and a terminal, for example, between a base station and a terminal; the sending and receiving of information can also be information exchange between two RAN nodes, for example, between a CU and a DU; the sending and receiving of information can also be information exchange between different modules within a device, for example, between a terminal chip and other modules in the terminal, or between a base station chip and other modules within the base station.

[0248] It is understood that the processor in the embodiments of the present application may be a central processor 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, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0249] The method steps in the embodiments of the present application can be implemented in hardware or in software instructions that can be executed by a processor. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory, flash memory, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, registers, hard disks, mobile hard disks, compact disc read-only memory (CD-ROM) or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. The storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in a base station or a terminal. The processor and the storage medium can also be present in a base station or a terminal as discrete components.

[0250] In the above embodiments, all or part of the embodiments may be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer programs or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of this application are performed in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, a network device, a user device, or other programmable device. The computer program or instructions may be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, the computer program or instructions may be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium may be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; an optical medium, such as a digital video disk; or a semiconductor medium, such as a solid-state drive. The computer-readable storage medium may be a volatile or nonvolatile storage medium, or may include both volatile and nonvolatile types of storage media.

[0251] Finally, regarding the embodiments of this application, there are the following points to explain:

[0252] First, in the embodiments of the present application, the first, second, and various numerical numbers are merely for the convenience of description and are not intended to limit the scope of the embodiments of the present application. For example, the first primary cell and the second primary cell represent two primary cells, which may be two different cells or the same cell.

[0253] Second, in the embodiments of the present application, "indication" may include direct indication and indirect indication, and may also include explicit indication and implicit indication. The information indicated by a certain information is called information to be indicated. In the specific implementation process, there are many ways to indicate the information to be indicated. For example, the information to be indicated can be directly indicated, such as the information to be indicated itself or the index of the information to be indicated. The information to be indicated can also be indirectly indicated by indicating other information, wherein there is an association relationship between the other information and the information to be indicated. It is also possible to indicate only a part of the information to be indicated, while the other parts of the information to be indicated are known or agreed in advance. For example, the indication of the information to be indicated can be achieved by means of a pre-agreed (such as a protocol provision) on whether a certain information element exists, thereby reducing the indication overhead to a certain extent.

[0254] Third, the "protocol" involved in the embodiments of this application may refer to a standard protocol in the communication field, for example, it may include an LTE protocol, an NR protocol, and related protocols in future communication systems, which is not limited in this application.

[0255] Fourth, "predefinition" or "preconfiguration" can be achieved by pre-saving corresponding codes, tables or other methods that can indicate relevant information in a device (for example, a terminal or base station). This application does not limit the specific implementation method. Among them, "saving" can mean saving in one or more memories, and the one or more memories can be separate settings or integrated in a processor or communication device; the one or more memories can also be partially set separately and partially integrated in a processor or communication device. The type of memory can be any form of storage medium, and this application is not limited to this.

[0256] Fifth, "at least one" means one or more, and "more" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist at the same time, where A and B can be single objects or multiple objects. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b and c can mean: a, or b, or c, or a and b, or a and c, or b and c, or a, b and c. Where a, b and c can be single objects or multiple objects respectively.

[0257] Sixth, in the embodiments of the present application, descriptions such as "when...", "in the case of...", "if" and "if" all mean that the device (for example, a terminal or base station) will perform corresponding processing under certain objective circumstances. It does not limit the time, nor does it require the device to perform a judgment action when implementing it, nor does it mean that there are other limitations.

[0258] Seventh, in the various embodiments of the present application, unless otherwise specified or provided by logic, the terms and / or descriptions between different embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

Claims

1. A method for switching a cell, characterized in that: The method is applied to a terminal, wherein a serving cell of the terminal includes a first primary cell and a first secondary cell, and the method includes: receiving first information, where the first information instructs the terminal to switch a primary cell from the first primary cell to a second primary cell, and the first information includes an identifier of the second secondary cell; According to the first information, a primary cell is switched from the first primary cell to the second primary cell, and a secondary cell is switched from the first secondary cell to the second secondary cell.

2. The method according to claim 1, characterized in that The method further comprises: receiving a downlink synchronization signal of the second secondary cell; Perform a cell search according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

3. The method according to claim 2, characterized in that The performing a cell search according to the downlink synchronization signal to obtain time-frequency synchronization of the second secondary cell includes: Before receiving the first information, a cell search is performed according to the downlink synchronization signal to obtain time and frequency synchronization of the second secondary cell.

4. The method according to any one of claims 1 to 3, characterized in that The method further comprises: receiving a reference signal of the second secondary cell; Channel state information is sent, where the channel state information is determined based on the reference signal.

5. The method according to claim 4, characterized in that The sending of channel state information comprises: The channel state information is sent before receiving the first information.

6. The method according to any one of claims 1 to 5, characterized in that The method further comprises: Second information is sent, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

7. The method according to any one of claims 1 to 6, characterized in that The first information further includes an identifier of the second primary cell, and the identifier of the second primary cell is the same as the identifier of the first primary cell.

8. A method for switching a cell, characterized in that: The method comprises: Sending first information, where the first information instructs the terminal to switch a primary cell from a first primary cell to a second primary cell, where the first information includes an identifier of a second secondary cell, and the first information further instructs the terminal to switch a secondary cell from the first secondary cell to the second secondary cell, where the first primary cell and the first secondary cell are serving cells of the terminal; A primary cell is switched from the first primary cell to the second primary cell, and a secondary cell is switched from the first secondary cell to the second secondary cell.

9. The method according to claim 8, characterized in that The method further comprises: Send a downlink synchronization signal of the second secondary cell.

10. The method according to claim 9, characterized in that The sending a downlink synchronization signal of the second secondary cell includes: Before sending the first information, a downlink synchronization signal of the second secondary cell is sent.

11. The method according to any one of claims 8 to 10, characterized in that The method further comprises: sending a reference signal of the second secondary cell; Channel state information is received, where the channel state information is determined based on the reference signal.

12. The method according to claim 11, characterized in that The sending a reference signal of the second secondary cell includes: Before sending the first information, a reference signal of the second secondary cell is sent.

13. The method according to any one of claims 8 to 12, characterized in that The method further comprises: Second information is received, where the second information indicates that the terminal supports simultaneous primary cell switching and secondary cell switching.

14. The method according to any one of claims 8 to 13, characterized in that The first information further includes an identifier of the second primary cell, and the identifier of the second primary cell is the same as the identifier of the first primary cell.

15. A communication device, characterized in that: include: A processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices and transmit them to the processor or to send signals from the processor to other communication devices, and the processor is used to implement the method as described in any one of claims 1 to 7 through a logic circuit or execute code instructions, or to implement the method as described in any one of claims 8 to 14.

16. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program or instructions, and when the computer program or instructions are executed by the communication device, the method according to any one of claims 1 to 7 is implemented, or the method according to any one of claims 8 to 14 is implemented.

Images