Communication method, apparatus and system

Abstract

The present application relates to the field of communications. Disclosed are a communication method, apparatus and system, aimed at addressing the problem of the uplink communication quality of terminal devices located at cell coverage edges being relatively poor, and thus the uplink communication quality no longer being sufficient to meet communication requirements in complex communication scenarios. The method comprises: an access network device transmitting a system information block (SIB) of a cell on a downlink carrier of the cell; a terminal device receiving the SIB of the cell on the downlink carrier of the cell, and on the basis of the received SIB, transmitting on an uplink carrier of the cell a random access request for accessing the cell; and the access network device receiving on the uplink carrier of the cell the random access request for accessing the cell, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier. The solution of the present application can be widely applied to the technical field of communications, and to fields such as artificial intelligence, Internet of Vehicles and smart home networking.

Description

Communication method, device and system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on January 31, 2024, with application number 202410142639.7 and application name “A Communication Method, Device and System”, 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 communication method, device, and system. Background Art

[0003] When a terminal device (also known as user equipment (UE)) accesses the network, it needs to connect to the cell corresponding to the base station. A cell refers to the area where a base station provides wireless communication services to terminal users. When a terminal device accesses a cell, the base station corresponding to the cell transmits downlink data on a downlink carrier, and the terminal device transmits uplink data on an uplink carrier. A downlink carrier refers to radio waves of a specific frequency that carry downlink data. An uplink carrier refers to radio waves of a specific frequency that carry uplink data.

[0004] However, with the development of communication technology, communication scenarios are becoming more and more complex. For terminal devices at the edge of cell coverage, there is a problem of poor uplink communication quality, which can no longer meet the communication needs in complex communication scenarios. Summary of the Invention

[0005] The embodiments of the present application provide a communication method, apparatus, and system to solve the problem of poor uplink communication quality for terminal devices at the edge of cell coverage, which can no longer meet communication needs in complex communication scenarios.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides a communication method, which can be executed by a terminal device or a functional module or chip within the terminal device. Taking execution by a terminal device as an example, the method includes: the terminal device receives a system information block (SIB) of the cell on a downlink carrier of the cell, and sends a random access request to access the cell on an uplink carrier of the cell based on the received SIB, wherein the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier.

[0008] Based on the method described in the first aspect, a terminal device can access a cell where the frequency band corresponding to the uplink carrier is different from the frequency band corresponding to the downlink carrier. Compared to a cell where the frequency band corresponding to the uplink carrier is the same as the frequency band corresponding to the downlink carrier, a cell where the frequency band corresponding to the uplink carrier is different from the frequency band corresponding to the downlink carrier can provide better uplink communication quality for the terminal device. For example, the frequency band corresponding to the uplink carrier of the new cell is a lower frequency band, and the frequency band corresponding to the downlink carrier of the new cell is a higher frequency band. The lower frequency band corresponding to the uplink carrier makes the uplink coverage range of the cell larger, thereby improving the uplink communication quality of the terminal device.

[0009] In one possible design, the SIB of the cell indicates that the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the cell is greater than a threshold.

[0010] Based on this possible design, the terminal device can determine that the frequency difference between the frequency band corresponding to the cell's uplink carrier and the frequency band corresponding to the cell's downlink carrier is greater than a threshold value based on the cell's SIB indication, implicitly indicating that the frequency band corresponding to the cell's uplink carrier and the frequency band corresponding to the cell's downlink carrier are both new frequency bands predefined by the protocol, thereby improving the flexibility of the cell's SIB indication of the cell's uplink carrier corresponding frequency band and the downlink carrier corresponding frequency band. The protocol predefines that the frequency difference between the uplink frequency band corresponding to the new frequency band and the downlink frequency band corresponding to the new frequency band is greater than a threshold value (for example, 1 GHz).

[0011] In one possible design, the protocol predefines a new frequency band, the SIB of the cell indicates that the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier of the cell are both predefined new frequency bands, and the terminal device can send a random access request to access the cell on the uplink carrier of the cell. The frequency difference between the uplink frequency band corresponding to the new frequency band and the downlink frequency band corresponding to the new frequency band is greater than a threshold (for example, 1GHz), and the duplex mode corresponding to the new frequency band is frequency division duplexing (FDD) or the first duplex mode. The first duplex mode refers to a duplex mode not defined in the existing protocol, such as supplementary uplink lite (SUL-lite).

[0012] Based on this possible design, a new frequency band predefined by a protocol is given, and the frequency difference between the uplink frequency band corresponding to the new frequency band and the downlink frequency band corresponding to the new frequency band is greater than a threshold value (for example, 1GHz). When the SIB of the cell indicates that the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier are both new frequency bands, the terminal device can also access the cell to improve the uplink communication quality. For example, the predefined new frequency band is the first frequency band, the uplink frequency band corresponding to the first frequency band is 869MHz-894MHz, and the downlink frequency band corresponding to the first frequency band is 4400MHz-5000MHz. When the SIB of the cell indicates that the frequency band corresponding to the uplink carrier supported by the cell and the frequency band corresponding to the downlink carrier are both the first frequency band, the terminal device accesses the cell and can obtain better uplink communication quality because the frequency band corresponding to the uplink carrier of the cell is a lower frequency band.

[0013] In one possible design, the SIB of a cell indicates the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell, and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell.

[0014] Based on this possible design, the terminal device can transmit uplink data on the uplink time domain resources indicated by the cell's SIB, and receive downlink data on the downlink time domain resources indicated by the cell's SIB. At this time, the uplink and downlink frame ratio of the time domain resources corresponding to the cell's uplink carrier indicated by the cell's SIB and the uplink and downlink frame ratio of the time domain resources corresponding to the cell's downlink carrier can be the same or different, so that the access network device corresponding to the cell can independently configure uplink time domain resources and downlink time domain resources for the terminal device, thereby improving resource utilization.

[0015] In one possible design, the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell is different from the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell.

[0016] Based on this possible design, when the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell is different from the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell, the terminal device can flexibly use the time domain resources corresponding to the uplink carrier of the cell and the time domain resources corresponding to the downlink carrier of the cell.

[0017] In a second aspect, an embodiment of the present application provides a communication method, which can be executed by an access network device or a functional module or chip within the access network device. Taking execution by the access network device as an example, the method includes: the access network device sends the SIB of the cell on the downlink carrier of the cell, and receives a random access request to access the cell on the uplink carrier of the cell, wherein the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier.

[0018] Based on the method described in the second aspect, a cell in which the frequency band corresponding to the uplink carrier corresponding to the access network device is different from the frequency band corresponding to the downlink carrier can provide services for the terminal device accessing the cell. At this time, the terminal device can flexibly access uplink carriers and downlink carriers of different frequency bands according to different business needs, and is no longer restricted to accessing a cell in which the frequency band corresponding to the uplink carrier is the same as the frequency band corresponding to the downlink carrier, providing more choices for the type of cell accessed by the terminal device.

[0019] In one possible design, the SIB of the cell indicates that the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the cell is greater than a threshold.

[0020] Based on this possible design, the access network equipment can indirectly achieve the effect of directly indicating that the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier of the cell by indicating that the frequency range of the uplink carrier of the cell is significantly different from the frequency range of the downlink carrier of the cell, so that the terminal equipment can flexibly access the cell where the frequency band corresponding to the uplink carrier is different from the frequency band corresponding to the downlink carrier.

[0021] In one possible design, the SIB of a cell indicates the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell, and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell.

[0022] Based on this possible design, the access network device can independently configure the cell's uplink time domain available resources and the cell's downlink time domain available resources for the terminal device. At the same time, the sum of the number of uplink available time domain resources and the number of downlink available time domain resources configured by the access network device is no longer restricted to being equal to the total number of time domain resources within a cycle. Therefore, the access network device can configure the appropriate cell's uplink time domain available resources and downlink time domain available resources for the terminal device based on the service requirements of the terminal device, thereby improving resource utilization.

[0023] In one possible design, the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell is different from the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell.

[0024] Based on this possible design, when the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell configured by the access network device is different from the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell, the terminal device can flexibly use the time domain resources corresponding to the uplink carrier of the cell and the time domain resources corresponding to the downlink carrier of the cell.

[0025] On the third aspect, an embodiment of the present application provides a communication method, which can be executed by a terminal device or a functional module or chip within the terminal device. Taking the execution of the terminal device as an example, the method includes: the terminal device receives a first indication information from an access network device corresponding to a first cell, and performs cell switching according to the cell switching method indicated by the first indication information, wherein the first indication information is used to indicate a cell switching method in which the uplink carrier is switched and the downlink carrier is not switched.

[0026] Based on this possible design, the terminal device can directly switch the uplink carrier according to the first indication information without switching the downlink carrier, so that the terminal device can switch from the first cell to the second cell according to the first indication information, saving the resource overhead of the terminal device. At the same time, the uplink carrier is switched according to the first indication information, while the downlink carrier is not switched, so that the switching process of the terminal device from the first cell to the second cell does not include downlink switching processes such as downlink synchronization and beam scanning, thereby saving the downlink terminal delay of the terminal device.

[0027] In one possible design, the terminal device sends uplink information to the first cell on a first uplink carrier, and receives downlink information of the first cell on a first downlink carrier; in response to switching from the first cell to the second cell, the terminal device sends uplink information to the second cell on the second uplink carrier, and receives downlink information of the second cell on the first downlink carrier; wherein the first uplink carrier is different from the second uplink carrier.

[0028] Based on this possible design, the terminal device can receive downlink information of the first cell or downlink information of the second cell on the first downlink carrier. When the terminal device responds to switching from the first cell to the second cell, the uplink carrier for transmitting uplink information of the terminal device is switched from the first carrier to the second uplink carrier, and the downlink carrier for receiving downlink information of the terminal device is still the first downlink carrier, so that the downlink link for receiving downlink information of the terminal device will not be interrupted during the process of switching from the first cell to the second cell, thereby reducing the delay of service interruption and achieving the reduction of cell switching delay.

[0029] In one possible design, the first indication information is carried in radio resource control (RRC) reconfiguration signaling, or the first indication information is carried in media access control control element (MAC CE) signaling, or the first indication information is carried in downlink control information (DCI).

[0030] Based on this possible design, various signalings that can be carried by the first indication information are given. In this way, different signalings are used to carry the first indication information for different scenarios, and this solution is flexibly and diversely applied to various communication scenarios to improve the utilization rate of the solution.

[0031] Fourthly, an embodiment of the present application provides a communication method, which can be executed by an access network device or a functional module or chip within the access network device. Taking execution by the access network device as an example, the method includes: obtaining first indication information, sending first indication information, wherein the first indication information is used to indicate a cell switching method in which the uplink carrier is switched and the downlink carrier is not switched.

[0032] Based on this possible design, the access network device sends a first indication message to the terminal device, so that the terminal device can switch the uplink carrier according to the instructions of the first indication message without switching the downlink carrier, thereby realizing switching from the first cell to the second cell, saving the terminal's resource overhead.

[0033] In one possible design, the first indication information is carried in radio resource control (RRC) reconfiguration signaling, or the first indication information is carried in media access control control element (MAC CE) signaling, or the first indication information is carried in downlink control information (DCI).

[0034] Based on this possible design, various signalings that can be carried by the first indication information are given. In this way, different signalings are used to carry the first indication information for different scenarios, and this solution is flexibly and diversely applied to various communication scenarios to improve the utilization rate of the solution.

[0035] In a fifth aspect, the present application provides a communication device, which may be a terminal device or a chip or system on chip in a terminal device, or a functional module in a terminal device for implementing the method in the first aspect or any possible design of the first aspect. The communication device can implement the functions performed by the terminal device in the above-mentioned first aspect or any possible design of the first aspect, and the functions can be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions. For example, the communication device may include a transceiver unit and a processing unit. Among them,

[0036] A transceiver unit, configured to receive the SIB of the cell on the downlink carrier of the cell;

[0037] The processing unit is configured to send a random access request for accessing the cell on an uplink carrier of the cell according to the SIB, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier.

[0038] Specifically, the execution actions of each unit of the communication device can refer to the first aspect or any possible design of the first aspect, and will not be repeated here.

[0039] In a sixth aspect, the present application provides a communication device, which may be an access network device or a chip or system on chip in an access network device, or a functional module in an access network device for implementing the second aspect or any possible design of the second aspect. The communication device may implement the functions performed by the access network device in the above-mentioned second aspect or any possible design of the second aspect, and the functions may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions. For example, the communication device may include a transceiver unit. Among them,

[0040] A transceiver unit, configured to send the SIB of the cell via the downlink carrier of the cell;

[0041] The transceiver unit is further configured to receive a random access request for accessing the cell on an uplink carrier of the cell, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier.

[0042] Specifically, the execution actions of each unit of the communication device can refer to the second aspect or any possible design of the second aspect, and will not be repeated here.

[0043] In the seventh aspect, the present application provides a communication device, which can be a terminal device or a chip or system on chip in the terminal device, and can also be a functional module in the terminal device for implementing the third aspect or any possible design of the third aspect. The communication device can implement the functions performed by the terminal device in the above-mentioned third aspect or any possible design of the third aspect, and the functions can be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions. For example, the communication device may include a transceiver unit and a processing unit. Among them,

[0044] a transceiver unit, configured to receive first indication information from an access network device corresponding to the first cell;

[0045] The processing unit is configured to perform cell switching according to a cell switching mode indicated by first indication information, wherein the first indication information is used to indicate a cell switching mode in which an uplink carrier is switched but a downlink carrier is not switched.

[0046] Specifically, the execution actions of each unit of the communication device can refer to the third aspect or any possible design of the third aspect, and will not be repeated here.

[0047] In an eighth aspect, the present application provides a communication device, which may be an access network device or a chip or system on chip in an access network device, or a functional module in an access network device for implementing the fourth aspect or any possible design of the fourth aspect. The communication device may implement the functions performed by the access network device in the above-mentioned fourth aspect or any possible design of the fourth aspect, and the functions may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions. For example, the communication device may include a processing unit and a transceiver unit. Among them,

[0048] A processing unit, configured to obtain first indication information;

[0049] The transceiver unit is configured to send first indication information; wherein the first indication information is used to indicate a cell switching mode in which an uplink carrier is switched but a downlink carrier is not switched.

[0050] Specifically, the execution actions of each unit of the communication device can refer to the fourth aspect or any possible design of the fourth aspect, and will not be repeated here.

[0051] In a ninth aspect, the present application provides a communication device. In one possible design, the communication device includes a processor and a communication interface. The processor and the communication interface are used to support the communication device to execute the communication method in the first aspect or any possible design of the first aspect, or the processor and the communication interface are used to support the communication device to execute the communication method in the second aspect or any possible design of the second aspect, or the processor and the communication interface are used to support the communication device to execute the communication method in the third aspect or any possible design of the third aspect, or the processor and the communication interface are used to support the communication device to execute the communication method in the fourth aspect or any possible design of the fourth aspect. In another possible design, the communication device may also include a memory for storing computer execution instructions and data necessary for the communication device. When the communication device is running, the processor executes the computer-executable instructions stored in the memory to enable the communication device to perform the communication method as described in the first aspect or any possible design of the first aspect, or to enable the communication device to perform the communication method as described in the second aspect or any possible design of the second aspect, to enable the communication device to perform the communication method as described in the third aspect or any possible design of the third aspect, to enable the communication device to perform the communication method as described in the fourth aspect or any possible design of the fourth aspect.

[0052] In the tenth aspect, the present application provides a communication system, which includes the communication device provided in the fifth aspect and the communication device provided in the sixth aspect; or, the communication system includes the communication device provided in the fifth aspect and the communication device provided in the ninth aspect; or, the communication system includes the communication device provided in the sixth aspect and the communication device provided in the ninth aspect; or, the communication system includes the communication device provided in the seventh aspect and the communication device provided in the eighth aspect; or, the communication system includes the communication device provided in the seventh aspect and the communication device provided in the ninth aspect; or, the communication system includes the communication device provided in the eighth aspect and the communication device provided in the ninth aspect.

[0053] In the eleventh aspect, the present application provides a computer-readable storage medium storing computer instructions, which, when the computer instructions are executed on a computer, enables the computer to execute the first aspect or any possible communication method in the design of the first aspect; or, enables the computer to execute the second aspect or any possible communication method in the design of the second aspect; or, enables the computer to execute the third aspect or any possible communication method in the design of the third aspect, or, enables the computer to execute the fourth aspect or any possible communication method in the design of the fourth aspect.

[0054] In a twelfth aspect, the present application provides a computer program product comprising computer instructions, which, when the computer instructions are run on a computer, cause the computer to execute the communication method of the first aspect or any possible design of the first aspect; or, cause the computer to execute the communication method of the second aspect or any possible design of the second aspect; or, cause the computer to execute the communication method of the third aspect or any possible design of the third aspect; or, cause the computer to execute the communication method of the fourth aspect or any possible design of the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a schematic diagram of frequency bands and uplink and downlink coverage;

[0056] Figure 2 is a schematic diagram of optimal uplink and optimal downlink for a cell edge terminal device;

[0057] FIG3 is a schematic diagram of a communication system provided in an embodiment of the present application;

[0058] FIG4 is a flow chart of a communication method provided by the present application;

[0059] FIG5 is a schematic diagram of a time domain uplink and downlink frame ratio corresponding to an uplink and downlink carrier provided by the present application;

[0060] FIG6 is a flow chart of a communication method provided in an embodiment of the present application;

[0061] FIG7 is a schematic diagram of frequency bands corresponding to uplink and downlink carriers of a cell provided in an embodiment of the present application;

[0062] Figure 8 is a schematic diagram of a cell defined in this NR;

[0063] FIG9 is a flow chart of a communication method provided by the present application;

[0064] FIG10 is a schematic structural diagram of a communication device provided by the present application;

[0065] FIG11 is a schematic structural diagram of a communication device provided by the present application;

[0066] FIG12 is a schematic structural diagram of a communication device provided by the present application;

[0067] FIG13 is a schematic structural diagram of a communication device provided by the present application;

[0068] FIG14 is a schematic structural diagram of a communication device provided in this application. DETAILED DESCRIPTION

[0069] Before introducing the embodiments of the present application, some technical terms involved in the embodiments of the present application are explained. It should be noted that the following explanations are intended to make the embodiments of the present application easier to understand and should not be regarded as limiting the scope of protection claimed by the embodiments of the present application.

[0070] A cell, also known as a cellular cell, refers to the area covered by a base station or part of a base station in a cellular mobile communication system. Terminal devices can access a cell to receive wireless communication services provided by the base station. A base station can correspond to one or more cells, which can be referred to as cells corresponding to the base station or cells of the base station, etc. A cell can correspond to an uplink carrier and a downlink carrier. The uplink carrier can be used by the terminal device to send uplink data and / or information to the base station corresponding to the cell, and the downlink carrier can be used by the base station corresponding to the cell to send downlink data and / or information to the terminal device. Downlink data and / or information are carried on radio waves of a specific frequency and transmitted to the terminal device through the base station antenna. The radio waves carrying downlink data are called downlink carriers. Uplink data and / or information are carried on radio waves of a specific frequency and transmitted to the base station through the terminal device antenna. The radio waves carrying uplink data are called uplink carriers.

[0071] The coverage of a cell is divided into uplink coverage and downlink coverage. Uplink coverage refers to the maximum distance or maximum range that a terminal device can reach when sending data to the base station corresponding to the cell, and can also be called the uplink transmission radiation range. Downlink coverage refers to the maximum distance or maximum range that a base station corresponding to the cell can reach when sending data to a terminal device, and can also be called the downlink transmission radiation range. The uplink coverage can be determined based on the uplink transmit power of the terminal device and / or the frequency band corresponding to the uplink carrier used by the terminal device. The greater the uplink transmit power of the terminal device, the greater the uplink coverage. The higher the frequency band corresponding to the uplink carrier used by the terminal device, the smaller the uplink coverage. It can be understood that the uplink transmit power of the terminal device is in direct proportion to the uplink coverage, and the frequency band corresponding to the uplink carrier is in inverse proportion to the uplink coverage. Similarly, the downlink coverage can be determined based on the downlink transmit power of the base station corresponding to the cell and / or the frequency band corresponding to the downlink carrier used by the base station corresponding to the cell. The greater the downlink transmit power of the base station corresponding to the cell, the greater the downlink coverage. The higher the frequency band corresponding to the downlink carrier used by the base station corresponding to the cell, the smaller the downlink coverage. It can be understood that the downlink transmit power of the base station corresponding to the cell is in direct proportion to the downlink coverage, and the frequency band corresponding to the downlink carrier is in inverse proportion to the downlink coverage. Due to the different communication capabilities and / or transmission capabilities between the terminal device and the base station, the uplink transmission power of the terminal device is different from the downlink transmission power of the base station. Even if the frequency band corresponding to the uplink carrier used by the terminal device and the frequency band corresponding to the downlink carrier used by the base station are the same, the uplink coverage and downlink coverage of the cell are different.

[0072] A frequency band refers to the applicable range and / or interval of the frequency of radio waves. Each frequency band has a fixed correspondence, that is, a fixed combination of the frequency band number (operating band), the corresponding uplink frequency band (uplink operating band), the corresponding downlink frequency band (downlink operating band), and the corresponding duplex mode (duplex mode) corresponding to a frequency band. The frequency band number is used to identify the frequency band, and the frequency band numbers corresponding to different frequency bands may be different. The uplink frequency band refers to the frequency range of the uplink carrier. The downlink frequency band refers to the frequency range of the downlink carrier. The duplex mode may include but is not limited to frequency division duplexing (FDD) and time division duplexing (TDD). Frequency division duplexing refers to the use of two symmetrical frequency channels to transmit uplink and downlink signals. Time division duplexing refers to the use of different time slots of the same frequency channel to transmit uplink and downlink signals. The uplink signal refers to the signal sent by the terminal device to the base station, and the corresponding base station receives the uplink signal. The downlink signal refers to the signal sent by the base station to the terminal device, and the corresponding terminal device receives the downlink signal.

[0073] For example, the 3rd Generation Partnership Project (3GPP) defines frequency bands for the New Radio (NR). Table 1 shows the frequency bands defined by NR.

[0074] Table 1

[0075] Since there is a fixed combination of the frequency band number, the corresponding uplink frequency band, the corresponding downlink frequency band, and the corresponding duplex mode corresponding to a frequency band, when the base station indicates that the frequency band corresponding to the uplink carrier of the cell is n1 and the frequency band corresponding to the downlink carrier of the cell is n1, the frequency range of the uplink band corresponding to the uplink carrier of the cell is 1920MHz-1980MHz, the frequency range of the downlink band corresponding to the downlink carrier of the cell is 2110MHz-2170MHz, and the duplex mode of the cell is frequency division duplex. Correspondingly, when the frequency range of the uplink band corresponding to the uplink carrier of the cell is 1920MHz-1980MHz, and the frequency range of the downlink band corresponding to the downlink carrier of the cell is 2110MHz-2170MHz, it can be understood that the frequency band corresponding to the uplink carrier of the cell is the same as the frequency band corresponding to the downlink carrier.

[0076] For example, assume that the frequency band corresponding to the uplink carrier used by the terminal device is the same as the frequency band corresponding to the downlink carrier used by the base station, and the uplink transmit power of the terminal device remains unchanged. Figure 1 shows a schematic diagram of the frequency band, uplink coverage, and downlink coverage. As shown in (a) of Figure 1, the terminal device accesses cell 1 corresponding to base station 1 with a downlink transmit power of P1, and cell 1 corresponds to frequency band F1. As shown in (b) of Figure 1, the terminal device accesses cell 2 corresponding to base station 2 with a downlink transmit power of P2 (P2 < P1), and cell 2 corresponds to frequency band F1. As shown in (c) of Figure 1, the terminal device accesses cell 3 corresponding to base station 3 with a downlink transmit power of P1, and cell 3 corresponds to frequency band F2 (F2 > F1). Comparing cell 1 with cell 2, the frequency band corresponding to cell 1 is the same as the frequency band corresponding to cell 2, and the downlink transmit power of base station 1 corresponding to cell 1 is greater than the downlink transmit power of base station 2 corresponding to cell 2. Therefore, the downlink coverage of cell 1 is greater than the downlink coverage of cell 2. The uplink transmit power of the terminal device corresponding to cell 1 is equal to the uplink transmit power of the terminal device corresponding to cell 2, and the uplink coverage of cell 1 is the same as the uplink coverage of cell 2. Comparing cell 1 with cell 3, the frequency band corresponding to cell 1 is less than the frequency band corresponding to cell 3, and the downlink transmit power of base station 1 corresponding to cell 1 is equal to the downlink transmit power of base station 3 corresponding to cell 3. At this time, the downlink coverage of cell 1 is greater than the downlink coverage of cell 3. The frequency band corresponding to cell 1 is less than the frequency band corresponding to cell 3, and the uplink transmit power of the terminal device corresponding to cell 1 is equal to the uplink transmit power of the terminal device corresponding to cell 3. The uplink coverage of cell 1 is greater than the uplink coverage of cell 3.

[0077] At present, the frequency band corresponding to the uplink carrier of the cell that the terminal device can access is the same as the frequency band corresponding to the downlink carrier. Therefore, the frequency difference between the frequency of the uplink band corresponding to the uplink carrier of the cell that the terminal device can access and the frequency of the downlink band corresponding to the downlink carrier of the cell (the lowest frequency or the highest frequency) is zero or small (for example, less than 1GHz). For example, the frequency band corresponding to the uplink carrier of the cell accessed by the terminal device and the frequency band corresponding to the downlink carrier are both the frequency bands identified by n51 in Table 1. At this time, the lowest frequency of the uplink band corresponding to the uplink carrier of the cell is 1472MHz, and the lowest frequency of the downlink band corresponding to the downlink carrier of the cell is 1472MHz. The lowest frequency of the uplink band corresponding to the uplink carrier of the cell is the same as the lowest frequency of the downlink band corresponding to the downlink carrier of the cell. Therefore, the terminal device can access the cell. For another example, the frequency band corresponding to the uplink carrier and the frequency band corresponding to the downlink carrier of the cell accessed by the terminal device are both the frequency band identified by n1 in Table 1. At this time, the lowest frequency of the uplink band corresponding to the uplink carrier of the cell is 1920 MHz, and the lowest frequency of the downlink band corresponding to the downlink carrier of the cell is 2110 MHz. The frequency difference between the lowest frequency of the uplink band corresponding to the uplink carrier and the lowest frequency of the downlink band corresponding to the downlink carrier of the cell is 90 MHz, so the terminal device can access the cell.

[0078] However, the uplink transmission power of the terminal device is lower than the downlink transmission power of the base station. The frequency band corresponding to the uplink carrier of the cell accessed by the terminal device is the same as the frequency band corresponding to the downlink carrier, which will cause a large difference between the uplink coverage and the downlink coverage, that is, the downlink coverage is greater than the uplink coverage. When the terminal device moves to the edge of the downlink coverage of the cell, the terminal device is no longer in the uplink coverage of the access cell. At this time, the uplink connection of the terminal device is not the optimal uplink, which affects the uplink communication quality of the terminal device.

[0079] For example, Figure 2 shows a schematic diagram of the optimal uplink and optimal downlink of a cell edge terminal device. In Figure 2, the cell currently providing services for the terminal device is cell 1 corresponding to base station 1. The uplink coverage in cell 1 is smaller than the downlink coverage. When the terminal device moves to an area in cell 1 where the downlink coverage does not overlap with the uplink coverage (uplink and downlink imbalance area), the cell that provides the optimal downlink for the terminal device is still cell 1, and the cell that provides the optimal uplink for the terminal device is changed from cell 1 to cell 2 corresponding to base station 2. Therefore, the uplink service quality provided by cell 1 to the terminal device in the uplink and downlink imbalance area in cell 1 is lower than the downlink quality, thereby affecting the uplink communication quality of the terminal device. Among them, the optimal uplink refers to the uplink link with the least path loss for the terminal device to send uplink data and / or information to the base station. The optimal downlink refers to the downlink link with the least path loss for the base station to send downlink data and / or information to the terminal device.

[0080] In order to solve the problem of poor uplink communication quality for terminal devices at the edge of cell coverage, which can no longer meet the communication needs in complex communication scenarios, the present application provides a communication method, which includes: an access network device sends the SIB of the cell on the downlink carrier of the cell, the terminal device receives the SIB of the cell on the downlink carrier of the cell, and according to the received SIB, sends a random access request for accessing the cell on the uplink carrier of the cell, and the access network device receives the random access request for accessing the cell on the uplink carrier of the cell, wherein the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier. In this way, the terminal device can access a cell whose uplink carrier corresponds to a frequency band different from the frequency band of the downlink carrier, so that the uplink connection and downlink connection of the terminal device can be optimized at the same time, thereby improving the uplink communication quality of the terminal user. At the same time, the terminal device can access uplink carriers and downlink carriers of different frequency bands according to different business needs. For example, when the business demand is large, the terminal device accesses an uplink carrier with a large bandwidth and a low frequency band and a downlink carrier with a high frequency band; when the delay requirement is low, the terminal device accesses an uplink carrier with a high frequency band and a downlink carrier with a low frequency band.

[0081] The communication method provided in the embodiments of the present application is described below with reference to the accompanying drawings.

[0082] The communication method provided in the embodiment of the present application can be used for the third generation partnership project (3GPP) communication system, for example, the long term evolution (LTE) system, and can also be a fifth generation (5G) mobile communication system, NR system, beyond 5G (B5G) mobile communication system, sixth generation (6G) mobile communication system, new air interface vehicle to everything (NR V2X) system, and can also be applied to a system of LTE and 5G hybrid networking, or a device-to-device (D2D) communication system, a machine-to-machine (M2M) communication system, the Internet of Things (IoT), and other next-generation communication systems, and can also be a non-3GPP communication system without limitation. The communication method provided in the embodiment of the present application is described below using the communication system shown in Figure 3 as an example.

[0083] The technical solutions of the embodiments of the present application can be applied to various communication scenarios, for example, one or more of the following communication scenarios: enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), machine type communication (MTC), massive machine type communications (mMTC), D2D, V2X, and IoT communication scenarios.

[0084] FIG3 is a schematic diagram of a communication system provided in an embodiment of the present application. As shown in FIG3 , the communication system 30 includes a terminal device and an access network device. It is understood that the devices in the communication system 30 can communicate directly with each other or through forwarding by other devices, and this embodiment of the present application does not specifically limit this.

[0085] It should be understood that Figure 3 is merely a schematic diagram and does not limit the applicable scenarios of the technical solutions provided in this application. Those skilled in the art will appreciate that, in a specific implementation, communication system 30 may include fewer devices than shown in Figure 3 , or may include other devices. The number of devices in communication system 30 may also be determined based on specific needs and is not limited. The following describes the devices in the system shown in Figure 3 .

[0086] Terminal equipment can be called a terminal, or user equipment (UE) or mobile station (MS) or mobile terminal (MT), etc., including handheld devices, vehicle-mounted devices, wearable devices or computing devices with wireless communication functions. Specifically, the terminal equipment can be a mobile phone, a tablet computer or a computer with wireless transceiver function, and can also be a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in unmanned driving, a wireless terminal in telemedicine, a wireless terminal in a smart grid, a wireless terminal in a smart city, a smart home, a vehicle-mounted terminal, etc. In the embodiment of the present application, the device for realizing the function of the terminal device can be a terminal device, or a device that can support the terminal device to realize the function, such as a chip system (such as a chip, or a processing system composed of multiple chips) or a modem. The following describes the communication method provided in the embodiment of the present application by taking the device for realizing the function of the terminal device as an example.

[0087] The access network device is mainly used to implement functions such as resource scheduling, wireless resource management, and wireless access control of terminal devices. It is a device in the radio access network (RAN) that connects terminal devices to the wireless network. The RAN can be connected to the core network (for example, it can be the core network of LTE or the core network of 5G). The access network device can be an evolved base station (eNB or eNodeB) in LTE, or a base station in a 5G network or a future evolved public land mobile network (PLMN), a broadband network gateway (BNG), an aggregation switch or a non-3GPP access device; or the access network device in the embodiment of the present application can also be a wireless controller in a cloud radio access network (CRAN); or a transmission and reception point (TRP), or a device including a TRP, etc., which is not specifically limited in the embodiment of the present application. Optionally, the access network device in the embodiment of the present application may include various forms of base stations, such as: macro base stations, micro base stations (also known as small stations), relay stations, access points, etc., and the embodiment of the present application does not specifically limit this. In the embodiment of the present application, the device for implementing the function of the access network device can be an access network device, or it can be a device that can support the access network device to implement the function, such as a chip system (such as a processing system composed of one chip or multiple chips) or a modem. The following describes the communication method provided in the embodiment of the present application by taking the device for implementing the function of the access network device as an example, which is a base station.

[0088] The following describes the communication method provided by the embodiments of the present application in conjunction with the communication system shown in Figure 3. The actions, terms, etc. involved in the following embodiments can refer to each other. The message names or parameter names in the messages exchanged between devices in each embodiment are only examples, and other names can also be used in specific implementations. For example, the word "corresponding" in the following embodiments can be replaced by "associating", and the word "sending" in the following embodiments can be replaced by "transmitting".

[0089] FIG4 is a flow chart of a communication method provided in an embodiment of the present application. As shown in FIG4 , the method may include steps S401 to S403:

[0090] S401: The access network device sends the SIB of the cell on the downlink carrier of the cell. Correspondingly, the terminal device receives the SIB of the cell on the downlink carrier of the cell.

[0091] Among them, SIB refers to a message sent by an access network device to a terminal device. The SIB may include information required for the terminal device to initialize, for example, information required for the terminal device to initially access a cell.

[0092] In the present application, the SIB of a cell may carry frequency band information such as the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier. The SIB of a cell may carry information such as the frequency band number corresponding to the frequency band corresponding to the uplink carrier of the cell, the frequency band number corresponding to the frequency band corresponding to the downlink carrier of the cell, and the frequency band number corresponding to the frequency band of the uplink and downlink carriers of the cell is the frequency band number corresponding to the first frequency band. Among them, the frequency band corresponding to the uplink and downlink carriers of the cell can be understood as when the frequency band corresponding to the uplink carrier of the cell is the same as the frequency band corresponding to the downlink carrier of the cell, the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier of the cell can be simply referred to as the frequency band corresponding to the uplink and downlink carriers of the cell.

[0093] In one possible scenario, when the SIB of a cell carries the frequency band number corresponding to the frequency band corresponding to the uplink carrier and the frequency band number corresponding to the frequency band corresponding to the downlink carrier, the terminal device can determine the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier of the cell based on the fixed combination of each band and its corresponding frequency band number, as well as the frequency band number corresponding to the frequency band corresponding to the uplink carrier indicated by the SIB of the cell and the frequency band number corresponding to the frequency band corresponding to the downlink carrier. At this time, the frequency band corresponding to the uplink carrier is the frequency band identified by the corresponding frequency band number, and the frequency band corresponding to the downlink carrier is the frequency band identified by the corresponding frequency band number.

[0094] For example, the SIB is SIB1, and the frequency band number corresponding to the frequency band of the uplink carrier carried by the SIB1 of the cell is n1, and the frequency band number corresponding to the frequency band of the downlink carrier is n1. At this time, the frequency band corresponding to the uplink carrier of the cell indicated by the SIB1 of the cell is the frequency band identified by n1, and the frequency band corresponding to the downlink carrier of the cell is the frequency band identified by n1.

[0095] The frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier of the cell.

[0096] In the present application, when the SIB of a cell carries the frequency band number corresponding to the frequency band corresponding to the uplink carrier of the cell and the frequency band number corresponding to the frequency band corresponding to the downlink carrier of the cell, the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier of the cell, and the frequency band number corresponding to the frequency band corresponding to the uplink carrier of the cell is different from the frequency band number corresponding to the frequency band corresponding to the downlink carrier of the cell.

[0097] For example, if the frequency band corresponding to the cell's uplink carrier carried by the SIB of the cell is n1, and the frequency band corresponding to the cell's downlink carrier carried by the SIB of the cell is n51, then the terminal device can directly determine that the frequency band corresponding to the cell's uplink carrier is different from the frequency band corresponding to the cell's downlink carrier. At this time, the uplink frequency band corresponding to the cell's uplink carrier is the same as the uplink frequency band corresponding to frequency band number n1, and the downlink frequency band corresponding to the cell's downlink carrier is the same as the downlink frequency band corresponding to frequency band number n51.

[0098] In another possible scenario, the frequency band number corresponding to the frequency band corresponding to the uplink and downlink carriers of the cell carried by the SIB of the cell is the frequency band number corresponding to the first frequency band. The first frequency band is a predefined new frequency band, the frequency band number corresponding to the new frequency band is a new frequency band number, and the duplex mode corresponding to the new frequency band can be FDD or the first duplex mode. As mentioned above, the new frequency band number refers to a frequency band number that has not appeared in the existing protocol (for example, n101), and the first duplex mode refers to a duplex mode that has not appeared in the existing protocol (for example, supplementary uplink lite (SUL-lite) mode). Optionally, the frequency difference between the uplink frequency band corresponding to the new frequency band and the downlink frequency band corresponding to the new frequency band is greater than a predefined threshold (for example, 1GHz). The subcarrier spacing set supported by the new frequency band is divided into an uplink subcarrier spacing set and a downlink subcarrier spacing set, and the two sets can be the same or different. The channel bandwidth of the new frequency band is divided into an uplink channel bandwidth and a downlink channel bandwidth. In the case of the same subcarrier, the uplink channel bandwidth and the downlink channel bandwidth can be the same or different.

[0099] For example, the first frequency band is a predefined new frequency band, the frequency band number corresponding to the first frequency band is n101, the uplink frequency band corresponding to the first frequency band is 869MHz-929MHz, the downlink frequency band corresponding to the first frequency band is 4400MHz-5000MHz, and the duplex mode corresponding to the first frequency band is the new SUL-lite. At this time, the SIB of the cell can carry the frequency band number corresponding to the uplink and downlink carriers of the cell, which is n101.

[0100] Among them, the SIB of the cell indicates that the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the cell is greater than a threshold value (for example, 1 GHz). At this time, the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the cell is greater than the threshold value (for example, 1 GHz). The frequency band corresponding to the uplink carrier of the corresponding cell and the frequency band corresponding to the downlink carrier are both new frequency bands predefined by the protocol. Among them, the protocol predefines that the frequency difference between the uplink frequency band corresponding to the new frequency band and the downlink frequency band corresponding to the new frequency band is greater than a threshold value (for example, 1 GHz). Therefore, the SIB of the cell indicates that the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the cell is greater than a threshold value (for example, 1 GHz), which implicitly indicates the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier.

[0101] For example, the protocol predefines that the frequency difference between the uplink frequency band corresponding to the new frequency band and the downlink frequency band corresponding to the new frequency band is greater than 1 GHz. If the SIB of the cell indicates that the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the cell is greater than 1 GHz, it can be determined that the frequency band corresponding to the uplink carrier of the cell and the frequency band corresponding to the downlink carrier of the cell are both new frequency bands.

[0102] Optionally, when the duplex mode corresponding to the new frequency band is predefined by the protocol as the only duplex mode, the SIB of the cell may indicate that the duplex mode corresponding to the frequency band corresponding to the uplink and downlink carriers of the cell is the only duplex mode. In this case, the only duplex mode can be used to uniquely identify the new frequency band, so the only duplex mode can implicitly indicate that the frequency band corresponding to the uplink and downlink carriers of the cell is the new frequency band.

[0103] For example, the first frequency band is a predefined new frequency band, the duplex mode corresponding to the first frequency band is SUL-lite, and the SIB of the cell may indicate the SUL-lite duplex mode corresponding to the frequency band corresponding to the uplink and downlink carriers of the cell. SUL-lite is a duplex mode that does not appear in existing protocols, and SUL-lite can be used to uniquely identify the first frequency band.

[0104] Optionally, in a possible situation, when the SIB of a cell indicates that the frequency band corresponding to the uplink and downlink carriers of the cell is a new frequency band predefined by the protocol, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell, and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier. The uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier is used to indicate the uplink time domain position in the uplink carrier for transmitting the uplink signal. The uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier is used to indicate the downlink time domain position in the downlink carrier for transmitting the downlink signal. Accordingly, the SIB of the cell can carry the time domain uplink and downlink frame ratio information corresponding to the uplink carrier of the cell, and the time domain uplink and downlink frame ratio information corresponding to the downlink carrier. The granularity of the time domain position can be frame, subframe, time slot and symbol.

[0105] For example, the base station corresponding to the cell configures available uplink time domain resources for the uplink carrier of the cell and available downlink time domain resources for the downlink carrier according to the time domain uplink and downlink frame ratio corresponding to the uplink and downlink carriers shown in Figure 5. At this time, the SIB of the cell carries the time domain uplink and downlink frame ratio information corresponding to the uplink carrier of the cell, which is 10:0. The granularity of the frame ratio is time slot, indicating that all 10 time slots on the uplink carrier of the cell can be used to transmit uplink signals; the time domain uplink and downlink frame ratio information corresponding to the downlink carrier of the cell is 8:2, indicating that the first 8 time slots on the downlink carrier of the cell can be used to transmit downlink signals, and the last two time slots cannot be used to transmit downlink signals. Accordingly, the terminal device transmits uplink signals in the uplink time domain resources indicated by the SIB of the cell, and transmits downlink signals in the downlink time domain resources indicated by the SIB of the cell.

[0106] Optionally, in another possible situation, when the SIB of the cell indicates the frequency band number corresponding to the frequency band corresponding to the uplink carrier of the cell, and the frequency band number corresponding to the frequency band corresponding to the downlink carrier of the cell, it is determined according to the duplex mode corresponding to the frequency band number corresponding to the frequency band corresponding to the uplink carrier of the cell, and the duplex mode corresponding to the frequency band number corresponding to the frequency band corresponding to the downlink carrier of the cell, whether the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell, and / or the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier.

[0107] Specifically, when the duplex mode corresponding to the frequency band corresponding to the frequency band number of the cell's uplink carrier is FDD, and the duplex mode corresponding to the frequency band number of the cell's downlink carrier is TDD, the cell's SIB is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the cell's downlink carrier. The time domain resources corresponding to the cell's uplink carrier default to full downlink.

[0108] For example, when the SIB of a cell indicates that the frequency band corresponding to the uplink carrier of the cell is n8, and the frequency band corresponding to the downlink carrier of the cell is n38, the duplex mode corresponding to the frequency band number n8 is FDD, and the duplex mode corresponding to the frequency band number n38 is TDD. Therefore, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier of the cell.

[0109] Specifically, when the duplex mode corresponding to the frequency band number corresponding to the frequency band corresponding to the uplink carrier of the cell is TDD, and the duplex mode corresponding to the frequency band number corresponding to the frequency band corresponding to the downlink carrier of the cell is TDD, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell, and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier.

[0110] For example, when the SIB of a cell indicates that the frequency band corresponding to the uplink carrier of the cell is n96 and the frequency band corresponding to the downlink carrier of the cell is n51, the duplex mode corresponding to the frequency band number n96 is TDD, and the duplex mode corresponding to the frequency band number n51 is TDD. Therefore, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier.

[0111] Specifically, when the duplex mode corresponding to the frequency band corresponding to the frequency band number of the cell's uplink carrier is TDD, and the duplex mode corresponding to the frequency band number of the cell's downlink carrier is FDD, the cell's SIB is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the cell's uplink carrier. The time domain resources corresponding to the cell's downlink carrier default to full downlink.

[0112] For example, when the SIB of a cell indicates that the frequency band corresponding to the uplink carrier of the cell is n96, and the frequency band corresponding to the downlink carrier of the cell is n94, the duplex mode corresponding to the frequency band number n96 is TDD, and the duplex mode corresponding to the frequency band number n94 is FDD. Therefore, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell.

[0113] Specifically, when the duplex mode corresponding to the frequency band corresponding to the frequency band number of the cell's uplink carrier is FDD, and the duplex mode corresponding to the frequency band number of the cell's downlink carrier is FDD, the cell's SIB is not used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the cell's uplink carrier, and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier. The time domain resources corresponding to the cell's uplink carrier default to all uplink, and the time domain resources corresponding to the downlink carrier default to all downlink.

[0114] For example, when the SIB of a cell indicates that the frequency band corresponding to the uplink carrier of the cell is n1, and the frequency band corresponding to the downlink carrier of the cell is n94, the duplex mode corresponding to the frequency band number n1 is FDD, and the duplex mode corresponding to the frequency band number n94 is FDD. Therefore, the SIB of the cell is not used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier of the cell.

[0115] S402: The terminal device sends a random access request to access the cell on the uplink carrier of the cell according to the received SIB.

[0116] Specifically, the terminal device determines whether a random access request to access the cell can be made on the uplink carrier of the cell based on the terminal device's capability information, the uplink frequency band corresponding to the uplink carrier of the cell, and the downlink frequency band corresponding to the downlink carrier of the cell. The uplink frequency band corresponding to the uplink carrier of the cell can be equivalently replaced by the uplink frequency band corresponding to the frequency band corresponding to the uplink carrier of the cell, and the downlink frequency band corresponding to the downlink carrier can be equivalently replaced by the downlink frequency band corresponding to the frequency band corresponding to the downlink carrier of the cell.

[0117] The capability information of the terminal device may include the frequency band information supported by the terminal device, or the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier and the lowest frequency of the frequency band corresponding to the downlink carrier in the cell supported by the terminal device.

[0118] The frequency band information supported by the terminal device may include at least one of the following information: frequency band number, uplink frequency band, downlink frequency band, and duplex mode. A detailed description of the frequency band number, uplink frequency band, downlink frequency band, and duplex mode can be found in the above description and will not be repeated here.

[0119] Specifically, when the capability information of the terminal device includes the frequency band information supported by the terminal device, the terminal device can determine the frequency band supported by the terminal device based on the frequency band information supported by the terminal device, and determine the uplink frequency band corresponding to the frequency band corresponding to the uplink carrier of the cell and the downlink frequency band corresponding to the frequency band corresponding to the downlink carrier according to the received SIB; when the uplink frequency band corresponding to the frequency band corresponding to the uplink carrier of the cell and the downlink frequency band corresponding to the frequency band corresponding to the downlink carrier are included in the frequency band supported by the terminal device, a random access request to access the cell is sent on the uplink carrier of the cell.

[0120] For example, the terminal device determines, based on the capability information of the terminal device, that the uplink frequency band corresponding to the frequency band supported by the terminal device is 869MHz-929MHz, and the downlink frequency band corresponding to the supported frequency band is 4400MHz-5000MHz. The frequency band corresponding to the uplink carrier of cell 1 carried by the SIB of cell 1 is the frequency band identified by n8, and the frequency band corresponding to the downlink carrier of cell 1 is the frequency band identified by n79. The terminal device determines, based on the SIB of cell 1, that the uplink frequency band corresponding to the frequency band of the uplink carrier of cell 1 is 880MHz-915MHz, and the downlink frequency band corresponding to the frequency band of the downlink carrier is 4400MHz-5000MHz. At this time, the uplink frequency band corresponding to the frequency band corresponding to the uplink carrier of cell 1 and the downlink frequency band corresponding to the frequency band corresponding to the downlink carrier are included in the frequency band supported by the terminal. Therefore, the terminal device can send a random access request to access cell 1 on the uplink carrier of cell 1.

[0121] Specifically, when the capability information of the terminal device includes the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell that is maximally supported by the terminal device and the lowest frequency of the frequency band corresponding to the downlink carrier, the terminal device can determine the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell supported by the terminal device and the lowest frequency of the frequency band corresponding to the downlink carrier based on the capability information of the terminal device. The terminal device determines whether the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier is less than or equal to the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell supported by the terminal device and the lowest frequency of the frequency band corresponding to the downlink carrier based on the frequency band information corresponding to the uplink carrier of the cell and the frequency band information corresponding to the downlink carrier. If the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of the cell and the lowest frequency of the frequency band corresponding to the downlink carrier is less than or equal to the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell supported by the terminal device and the lowest frequency of the frequency band corresponding to the downlink carrier, the terminal device can make a random access request to access the cell on the uplink carrier of the cell.

[0122] For example, the terminal device determines, based on the capability information of the terminal device, that the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell supported by the terminal and the lowest frequency of the frequency band corresponding to the downlink carrier is 1 GHz, the uplink frequency band corresponding to the frequency band of the uplink carrier of cell 1 carried by the SIB of cell 1 is 824 MHz-849 MHz, and the downlink frequency band corresponding to the frequency band of the downlink carrier is in the frequency range of 1995 MHz-2000 MHz. At this time, the frequency difference between the lowest frequency of the uplink frequency band corresponding to the frequency band corresponding to the uplink carrier of cell 1 and the lowest frequency of the downlink frequency band corresponding to the frequency band corresponding to the downlink carrier is 1171 MHz; at this time, the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier of cell 1 and the lowest frequency of the frequency band corresponding to the downlink carrier is less than the maximum frequency difference of 1 GHz between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell supported by the terminal device and the lowest frequency of the frequency band corresponding to the downlink carrier. The terminal device can make a random access request to access the cell on the uplink carrier of cell 1.

[0123] S403: The access network device receives a random access request for accessing the cell on the uplink carrier of the cell.

[0124] The access network device is an access network device corresponding to a cell where a frequency band corresponding to an uplink carrier is different from a frequency band corresponding to a downlink carrier.

[0125] Specifically, after the access network device receives a random access request sent by the terminal device on the uplink carrier of the cell, which accesses a cell whose frequency band corresponding to the uplink carrier is different from the frequency band corresponding to the downlink carrier, it allocates terminal device-specific resources to the terminal device, so that the terminal device successfully accesses the cell.

[0126] Based on the communication method shown in FIG4 , the terminal device can access a cell with a frequency band corresponding to the uplink carrier and a frequency band corresponding to the downlink carrier that are different. In this way, the terminal device can access a cell with an uplink carrier in a low frequency band and a downlink carrier in a high frequency band, and at the same time, the uplink connection and downlink connection of the terminal device can be optimized at the same time, thereby improving the uplink communication quality of the terminal user. At the same time, the terminal device can access uplink carriers of different frequency bands according to different business needs. For example, when the business demand is large, the terminal device accesses an uplink carrier with a low frequency band and a large bandwidth; when the latency requirement is low, the terminal device accesses an uplink carrier with a high frequency band.

[0127] Below, taking the terminal device as the terminal, the access network device as the base station, the terminal is within the wireless coverage of cell 1 and cell 2, cell 1 and cell 2 share downlink carrier 1, the reference signal receiving power (RSRP) of cell 1 is less than the RSRP of cell 2, base station 1 corresponds to cell 1, and base station 2 corresponds to cell 2 as an example, the communication method shown in Figure 4 is described in detail in combination with Figure 6.

[0128] FIG6 is a flow chart of a communication method provided in an embodiment of the present application. As shown in FIG6 , the method may include:

[0129] S601: Base station 1 sends synchronization signal block 1 to the terminal via a broadcast channel, and base station 2 sends synchronization signal block 2 to the terminal via a broadcast channel. Accordingly, the terminal receives synchronization signal block 1 and synchronization signal block 2.

[0130] The broadcast channel refers to a channel through which the base station sends messages to all terminal users in a cell, and is a public channel.

[0131] Among them, synchronization signal block 1 (system synchronization block 1, SSB1) corresponds to cell 1, and is used for the terminal and cell 1 to obtain time synchronization and frequency synchronization; synchronization signal block 2 (system synchronization block 2, SSB2) corresponds to cell 2, and is used for the terminal and cell 2 to obtain time synchronization and frequency synchronization.

[0132] Among them, cell 1 and cell 2 share downlink carrier 1, that is, the frequency of downlink carrier 1 of cell 1 is the same as the frequency of downlink carrier 1 of cell 2, and the frequency band corresponding to downlink carrier 1 of cell 1 is the same as the frequency band corresponding to downlink carrier 2 corresponding to cell 2.

[0133] For example, FIG7 is a schematic diagram of the frequency bands corresponding to the uplink and downlink carriers of a cell. In FIG7 , the available uplink carrier in cell 1 is uplink carrier 1, and the frequency band corresponding to uplink carrier 1 is frequency band 1. The available downlink carrier in cell 1 is downlink carrier 1, and the frequency band corresponding to downlink carrier 1 is frequency band 1. In FIG7 , the available uplink carrier in cell 2 is uplink carrier 2, and the frequency band corresponding to uplink carrier 2 is frequency band 2. The available downlink carrier in cell 2 is downlink carrier 1, and the frequency band corresponding to downlink carrier 1 is frequency band 1.

[0134] In this application, base station 1 corresponding to cell 1 and base station 2 corresponding to cell 2 may be the same base station or different base stations.

[0135] S602: The terminal determines SSB2 with good access signal quality based on the signal quality of synchronization signal block 1 and synchronization signal block 2.

[0136] Specifically, the terminal compares the RSRP corresponding to SSB1 with the RSRP corresponding to SSB2. If the RSRP corresponding to SSB2 is greater, the terminal accesses SSB2 with better signal quality. RSRP is a key parameter in wireless networks that represents wireless signal strength and quality, and is also a required physical layer measurement. The larger the RSRP, the better the signal quality.

[0137] Among them, SSB2 carries the control information corresponding to the system information block 1 (SIB1) of cell 2. Therefore, after the terminal parses SSB2, it can obtain the SIB1 of cell 2. The SIB1 of cell 2 can carry the information required for the terminal to access cell 2, such as the frequency band information corresponding to the uplink and downlink carriers of the cell.

[0138] S603: After parsing SSB2, the terminal obtains the frequency band information carried by SIB1 of cell 2 on downlink carrier 1.

[0139] Among them, the process of terminal parsing SSB2 is an existing technology and will not be repeated here.

[0140] The frequency band information carried by the SIB1 of cell 2 may be used to indicate that the frequency band corresponding to the uplink carrier 2 of cell 2 is frequency band 2, and the frequency band corresponding to the downlink carrier 1 is frequency band 1.

[0141] Specifically, the frequency band information carried by the SIB1 of cell 2 may include: the frequency band number corresponding to frequency band 2 corresponding to uplink carrier 2, and the frequency band number corresponding to frequency band 1 corresponding to downlink carrier 1.

[0142] Similarly, the frequency band information that can be carried by SIB1 of cell 1 may include: the frequency band number corresponding to frequency band 1 corresponding to uplink carrier 1, and the frequency band number corresponding to frequency band 1 corresponding to downlink carrier 1.

[0143] Optionally, the SIB1 of cell 2 carries the frequency band number corresponding to the frequency band 2 corresponding to the uplink carrier 2, and the frequency band number corresponding to the frequency band 1 corresponding to the downlink carrier 1. When the duplex mode corresponding to the frequency band number corresponding to the frequency band 2 corresponding to the uplink carrier 2 of cell 2 is TDD, and the duplex mode corresponding to the frequency band number corresponding to the frequency band 1 corresponding to the downlink carrier 1 of cell 2 is TDD, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to the uplink carrier 2 of cell 2, and the uplink and downlink frame ratio of the time domain resources corresponding to the downlink carrier 1. Among them, the time domain uplink and downlink frame ratio information corresponding to the uplink carrier 2 of cell 2 can be used to indicate the uplink time slot position for transmitting uplink data in the uplink carrier 2 within a period. The time domain uplink and downlink frame ratio information corresponding to the downlink carrier 1 of cell 2 can be used to indicate the downlink time slot position for transmitting downlink data in the downlink carrier 1.

[0144] Optionally, SIB1 of cell 2 carries the frequency band number corresponding to frequency band 2 corresponding to uplink carrier 2, and the frequency band number corresponding to frequency band 1 corresponding to downlink carrier 1. When the duplex mode corresponding to the frequency band number corresponding to frequency band 2 corresponding to uplink carrier 2 of cell 2 is TDD, and the duplex mode corresponding to the frequency band number corresponding to frequency band 1 corresponding to downlink carrier 1 of cell 2 is FDD, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to uplink carrier 2 of cell 2. Among them, the time domain uplink and downlink frame ratio information corresponding to uplink carrier 2 of cell 2 can be used to indicate the uplink time slot position for transmitting uplink data in uplink carrier 2 within a period.

[0145] Optionally, SIB1 of cell 2 carries the frequency band number corresponding to frequency band 2 corresponding to uplink carrier 2, and the frequency band number corresponding to frequency band 1 corresponding to downlink carrier 1. When the duplex mode corresponding to the frequency band number corresponding to frequency band 2 corresponding to uplink carrier 2 of cell 2 is FDD, and the duplex mode corresponding to the frequency band number corresponding to frequency band 1 corresponding to downlink carrier 1 of cell 2 is TDD, the SIB of the cell is also used to indicate the uplink and downlink frame ratio of the time domain resources corresponding to downlink carrier 1 of cell 2. The time domain uplink and downlink frame ratio information corresponding to downlink carrier 1 of cell 2 can be used to indicate the downlink time slot position for transmitting downlink data in downlink carrier 1.

[0146] S604: The terminal determines whether it can access cell 2 according to the terminal capability information, frequency band 2 corresponding to uplink carrier 2 and frequency band 1 corresponding to downlink carrier 1 indicated by SIB1 of cell 2.

[0147] For the description of the capability information of the terminal, reference may be made to the description of the capability information of the terminal device in S402 , which will not be repeated here.

[0148] In one possible scenario, when the capability information of the terminal includes the frequency band information supported by the terminal, the terminal can determine the frequency band supported by the terminal based on the frequency band information supported by the terminal, and the frequency band supported by the terminal can be used to determine the uplink frequency band supported by the terminal and the supported downlink frequency band; the terminal determines whether the uplink frequency band corresponding to frequency band 2 corresponding to uplink carrier 2 of cell 2 is included in the uplink frequency band supported by the terminal, and whether the downlink frequency band corresponding to frequency band 1 corresponding to downlink carrier 1 of cell 2 is included in the downlink frequency band supported by the terminal based on frequency band 2 corresponding to uplink carrier 2 and frequency band 1 corresponding to downlink carrier 1 indicated by SIB1 of cell 2; when the uplink frequency band corresponding to frequency band 2 corresponding to uplink carrier 2 of cell 2 is included in the uplink frequency band supported by the terminal, and the downlink frequency band corresponding to frequency band 1 corresponding to downlink carrier 1 of cell 2 is included in the downlink frequency band supported by the terminal, the terminal can access cell 2. If the uplink frequency band corresponding to the frequency band 2 of the uplink carrier 2 of cell 2 is not within the uplink frequency band supported by the terminal, and the downlink frequency band corresponding to the frequency band 1 of the downlink carrier 1 of cell 2 is not within the downlink frequency band supported by the terminal, the terminal cannot access cell 2.

[0149] For example, based on the terminal's capability information, the terminal determines that the uplink frequency band supported by the terminal is 869MHz-929MHz, and the downlink frequency band is 4400MHz-5000MHz. The SIB1 of cell 2 indicates that the uplink frequency band corresponding to frequency band 2 of uplink carrier 2 of cell 2 is 880MHz-915MHz, and the downlink frequency band corresponding to frequency band 1 of downlink carrier 1 is 4400MHz-5000MHz. At this time, the uplink frequency band supported by the terminal includes the uplink frequency band corresponding to frequency band 2 corresponding to uplink carrier 2, and the downlink frequency band supported by the terminal includes the downlink frequency band corresponding to frequency band 1 corresponding to downlink carrier 1. Therefore, the terminal can access cell 2.

[0150] In another possible situation, when the capability information of the terminal includes the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell that is maximally supported by the terminal and the lowest frequency of the frequency band corresponding to the downlink carrier, the terminal can determine the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell supported by the terminal and the lowest frequency of the frequency band corresponding to the downlink carrier according to the capability information of the terminal; the terminal determines the lowest frequency of the uplink frequency band corresponding to the frequency band 2 of the uplink carrier 2 of the cell 2 and the lowest frequency of the downlink carrier according to the frequency band 2 corresponding to the uplink carrier 2 and the frequency band 1 corresponding to the downlink carrier 1 indicated by SIB1 of cell 2. Whether the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier 2 and the lowest frequency of the frequency band corresponding to the downlink carrier in the cell supported by the terminal is less than or equal to the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier and the lowest frequency of the frequency band corresponding to the downlink carrier in the cell supported by the terminal; when the frequency difference between the lowest frequency of the frequency band 2 corresponding to the uplink carrier 2 of cell 2 and the lowest frequency of the frequency band 1 corresponding to the downlink carrier 1 is less than or equal to the maximum frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier and the lowest frequency of the frequency band corresponding to the downlink carrier in the cell supported by the terminal, the terminal can access cell 2; otherwise, the terminal cannot access cell 2.

[0151] For example, the terminal determines, based on the terminal's capability information, that the frequency difference between the lowest frequency of the frequency band corresponding to the uplink carrier in the cell that the terminal supports the most and the lowest frequency of the frequency band corresponding to the downlink carrier is 1 GHz. SIB1 of cell 2 indicates that the lowest frequency of the uplink frequency band corresponding to frequency band 2 of uplink carrier 2 of cell 2 is 824 MHz, and the lowest frequency of the downlink frequency band corresponding to frequency band 1 of downlink carrier 1 is 1995 MHz. The frequency difference between the lowest frequency of the uplink frequency band corresponding to frequency band 2 of uplink carrier 2 of cell 2 and the lowest frequency of the downlink frequency band corresponding to frequency band 1 of downlink carrier 1 is 1171 MHz, which is less than 1 GHz. Therefore, the terminal can access cell 2.

[0152] S605: When the terminal determines that it can access cell 2, it sends a random access request for accessing cell 2 to base station 2 on uplink carrier 2. Correspondingly, base station 2 receives the random access request for accessing cell 2 on uplink carrier 2.

[0153] The terminal sending a random access request to access cell 2 to base station 2 on uplink carrier 2 is a prior art and will not be described in detail here.

[0154] Optionally, when the terminal determines that it cannot access cell 2, it re-determines an accessible cell.

[0155] Based on the communication method shown in FIG5 , when a terminal is within the wireless coverage of cell 1 and cell 2, cell 1 and cell 2 share downlink carrier 1, and the RSRP of cell 1 is less than the RSRP of cell 2, the terminal first determines whether it can access cell 2, and the frequency band corresponding to the uplink carrier in cell 2 is different from the frequency band corresponding to the downlink carrier. When the terminal determines that the terminal can access cell 2 based on the terminal's capability information, the frequency band corresponding to the uplink carrier in the cell indicated by SIB1 of cell 2, and the frequency band corresponding to the downlink carrier, the terminal is no longer restricted to accessing a cell (e.g., cell 1) in which the frequency band corresponding to the uplink carrier is the same as the frequency band corresponding to the downlink carrier, so that the terminal can access cell 2 in which the frequency band corresponding to the uplink carrier is different from the frequency band corresponding to the downlink carrier according to service requirements. For example, when the service demand is large, the terminal accesses a cell with a low-frequency uplink carrier and a high-frequency downlink carrier, thereby improving the uplink communication quality of the terminal user.

[0156] On the other hand, cell switching refers to the movement of a terminal device from one cell to another while it is connected and maintaining data transmission services, or when the original serving cell (source cell) can no longer provide services to the terminal device due to factors such as wireless transmission service load adjustment, activation operation maintenance, and equipment failure. In order to maintain data transmission services and service quality, the wireless bearer system will search for the most suitable cell (target cell) or network to continue to provide uninterrupted services to the terminal device, thereby realizing mobility management with seamless wireless network coverage.

[0157] Based on the duplex mode for transmitting uplink and downlink data within the cell, cells can be divided into FDD cells, TDD cells, and supplementary uplink (SUL) cells. An FDD cell refers to a cell in which the duplex mode for transmitting uplink and downlink data simultaneously is the FDD mode. In this case, the frequency band corresponding to the uplink and downlink carriers in the cell is the FDD band. A TDD cell refers to a cell in which the duplex mode for transmitting uplink and downlink data is the TDD mode. In this case, the frequency band corresponding to the uplink and downlink carriers in the cell is the TDD band. A SUL cell refers to a cell in which a SUL carrier exists. The frequency band corresponding to the SUL carrier is the SUL band. Among them, the SUL carrier in the lower frequency band can be used to enhance the uplink coverage of the cell.

[0158] For example, Figure 8 shows a schematic diagram of a cell defined by NR. In Figure 8, the FDD cell includes 1 uplink carrier and 1 downlink carrier, and the uplink carrier and the downlink carrier correspond to one FDD frequency band; the TDD cell includes 1 uplink carrier and 1 downlink carrier, and the uplink carrier and the downlink carrier correspond to one TDD frequency band; the SUL cell includes 1 downlink carrier, 1 normal uplink carrier, and one SUL carrier, where the normal uplink carrier and the downlink carrier correspond to one TDD frequency band, and the SUL carrier corresponds to one SUL frequency band.

[0159] When the terminal device moves to the coverage edge of the source cell that provides service for it, in order to ensure that the terminal device can continuously access the network, the terminal device needs to switch from the source cell to the target cell. Among them, the frequency band corresponding to the uplink carrier in the source cell is the same as the frequency band corresponding to the downlink carrier, and the frequency band corresponding to the uplink carrier in the target cell is the same as the frequency band corresponding to the downlink carrier. When the frequency band corresponding to the uplink and downlink carriers in the source cell is different from the frequency band corresponding to the uplink and downlink carriers of the target cell, when the terminal device switches from the source cell to the target cell, both the uplink carrier and the downlink carrier will be switched, resulting in a long cell switching time for the terminal device and poor communication quality for the terminal user. For example, when the terminal device switches from the FDD cell in Figure 8 to the TDD cell in Figure 8, the downlink carrier of the FDD frequency band in the FDD cell needs to be switched to the downlink carrier of the TDD frequency band in the TDD cell, and the uplink carrier of the FDD frequency band in the FDD cell needs to be switched to the uplink carrier of the TDD frequency band in the TDD cell. There is a long switching time and poor communication quality for the terminal user.

[0160] In order to solve the problem that when a terminal device switches from a source cell to a target cell, both the uplink carrier and the downlink carrier will be switched, resulting in a long cell switching time for the terminal device and poor communication quality for the terminal user, the present application provides a communication method, which includes: the access network device obtains first indication information indicating a cell switching method, sends the first indication information to the terminal device, the terminal device receives the first indication information from the access network device, and performs cell switching according to the cell switching method indicated by the first indication information. In this way, the terminal device can implement cell switching according to the cell switching method indicated by the first indication information. In the case where the cell switching method indicated by the first indication information is that the downlink carrier is not switched and the uplink carrier is switched, the uplink access process can be reduced, the downlink link of the downlink data and / or information sent by the access network device to the terminal device will not be interrupted, the delay of the terminal device accessing the service is reduced, the user plane is not reconfigured, and the delay of cell switching is reduced.

[0161] The following describes the communication method provided by the embodiments of the present application in conjunction with the communication system shown in Figure 3. The actions, terms, etc. involved in the following embodiments can refer to each other. The message names or parameter names in the messages exchanged between devices in each embodiment are only examples, and other names can also be used in specific implementations. For example, the word "corresponding" in the following embodiments can be replaced by "associating", and the word "sending" in the following embodiments can be replaced by "transmitting".

[0162] FIG9 is a flow chart of a communication method provided in an embodiment of the present application. As shown in FIG9 , the method may include steps S901-S902:

[0163] S901: The access network device obtains first indication information indicating a cell switching mode and sends the first indication information to the terminal device. Accordingly, the terminal device receives the first indication information indicating a cell switching mode from the access network device.

[0164] The access network device obtaining the first indication information indicating the cell switching method may include: the access network device triggering the acquisition of the first indication information indicating the cell switching method. For example, the access network device detects that the signal strength of the current uplink reference signal is lower than a threshold or the signal quality of the current uplink reference signal is lower than a threshold, which triggers the access network device to obtain the first indication information indicating the cell switching method. For another example, the access network device receives a handover request from a terminal device, which triggers the access network device to obtain the first indication information indicating the cell switching method.

[0165] Among them, the cell switching mode indicated by the first indication information includes: downlink carrier not switching, uplink carrier switching, or downlink carrier switching, uplink carrier switching. In the case where the first indication information indicates that the cell switching mode is downlink carrier not switching and uplink carrier switching, since the downlink carrier is not switched, the process of the terminal device performing cell switching includes an uplink synchronization process (for example, the terminal device sends a random access request to the target cell). In the case where the first indication information indicates that the cell switching mode is downlink carrier switching and uplink carrier switching, the terminal device performs cell switching according to the existing cell switching process (for example, downlink synchronization, beam scanning, channel measurement, uplink synchronization, etc.).

[0166] In one example, the first indication information can be carried in radio resource control (RRC) reconfiguration signaling, or carried in medium access control control element (MAC CE) signaling, or carried in downlink control information (DCI), that is, a direct indication method can be used to indicate to the terminal device how to perform cell switching.

[0167] In another example, the access network device sends indication information of the cell to be switched to the terminal device. For example, the terminal device receives the indication information of the cell to be switched from the access network device, determines the target cell based on the indication information of the cell to be switched, and compares whether the frequency of the downlink carrier of the source cell is the same as the frequency of the downlink carrier of the target cell. If the frequency of the downlink carrier of the source cell is the same as the frequency of the downlink carrier of the target cell, the terminal device performs a cell switching method in which the downlink carrier is not switched and the uplink carrier is switched; conversely, if the frequency of the downlink carrier of the source cell is different from the frequency of the downlink carrier of the target cell, the terminal device performs a cell switching method in which the downlink carrier is switched and the uplink carrier is switched.

[0168] For example, the cell currently providing services to the terminal device is cell 1, the frequency of the downlink carrier of cell 1 is 2110MHz, the frequency of the downlink carrier of cell 2 is 2110MHz, and the frequency of the downlink carrier of cell 3 is 1472MHz. When the indication information of the switching cell sent by the base station 1 corresponding to cell 1 to the terminal device indicates that the cell to be switched by the terminal device is cell 2, the terminal device performs cell switching by uplink carrier switching, and the downlink carrier is not switched. When the indication information of the switching cell sent by the base station 1 corresponding to cell 1 to the terminal device indicates that the cell to be switched by the terminal device is cell 3, the terminal device performs cell switching by uplink carrier switching and downlink carrier switching.

[0169] In another example, the predefined terminal device determines the cell switching mode of the terminal device based on the frequency difference between the lowest frequency (or the highest frequency) of the frequency band corresponding to the downlink carrier of the source cell (the cell that provides services to the terminal device before switching) and the lowest frequency (or the highest frequency) of the frequency band corresponding to the downlink carrier of the target cell (the cell that provides services to the terminal device after switching).

[0170] For example, if the frequency difference between the lowest frequency of the frequency band corresponding to the downlink carrier of the predefined source cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the target cell is zero, the terminal device determines that the mode of this cell switching is not to switch the downlink carrier but to switch the uplink carrier; otherwise, the terminal device determines that the mode of this cell switching is to switch the downlink carrier and the uplink carrier. Alternatively, if the frequency difference between the highest frequency of the frequency band corresponding to the downlink carrier of the predefined source cell and the highest frequency of the frequency band corresponding to the downlink carrier of the target cell is zero, the terminal device determines that the mode of this cell switching is not to switch the downlink carrier but to switch the uplink carrier; otherwise, the terminal device determines that the mode of this cell switching is to switch the downlink carrier and the uplink carrier.

[0171] As mentioned above, the indication information of the cell to which the terminal device switches determines the cell switching method, and / or the terminal device is predefined to determine the cell switching method based on the frequency difference between the lowest frequency of the frequency band corresponding to the downlink carrier of the source cell and the lowest frequency of the frequency band corresponding to the downlink carrier of the target cell, and / or the terminal device is predefined to determine the cell switching method based on the frequency difference between the highest frequency of the frequency band corresponding to the downlink carrier of the source cell and the highest frequency of the frequency band corresponding to the downlink carrier of the target cell, that is, an implicit indication method can be used to indicate to the terminal device how to perform cell switching.

[0172] S902: The terminal device performs cell switching according to the cell switching method indicated by the first indication information.

[0173] Specifically, the terminal device performs cell switching according to the cell switching method indicated by the first indication information, including: when the first indication information indicates that the cell switching method is uplink carrier switching and the downlink carrier is not switched, the terminal device sends uplink information to the first cell on the first uplink carrier, and receives downlink information of the first cell on the first downlink carrier; in response to switching from the first cell to the second cell, the terminal device sends uplink information to the second cell on the second uplink carrier, and receives downlink information of the second cell on the first downlink carrier; wherein the first uplink carrier is different from the second uplink carrier. Among them, the first uplink carrier is an available uplink carrier of the first cell, the first downlink carrier is an available downlink carrier of the first cell, the second uplink carrier is an available uplink carrier of the second cell, and the first downlink carrier may also be an available downlink carrier of the second cell. The first cell can be alternatively described as a source cell, and the second cell can be alternatively described as a target cell.

[0174] The terminal device receives downlink information of the first cell or receives downlink information of the second cell through the first downlink carrier, so that the downlink communication link of the terminal device will not be interrupted.

[0175] Based on the communication method shown in Figure 9, the terminal device can perform cell switching in accordance with the cell switching method directly indicated by the first indication information, or implicitly indicate the cell switching method of the terminal device, providing more options for indicating the cell switching method of the terminal device. At the same time, when the cell switching method indicated by the first indication information is that the downlink carrier is not switched but the uplink carrier is switched, the terminal device can maintain the downlink uninterrupted, reduce the delay of service interruption, and achieve the reduction of the delay of cell switching.

[0176] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of interaction between various devices. It is understandable that, in order to realize the above functions, each device, such as a terminal device, an access network device, etc., includes a hardware structure and / or software module corresponding to the execution of each function. Those skilled in the art should easily realize that, in combination with the 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.

[0177] In the embodiments of the present application, functional modules of terminal devices, access network devices, etc. can be grouped according to the above-mentioned method examples. For example, each functional module can be grouped according to each function, or two or more functions can be integrated into one processing module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the grouping of modules in the embodiments of the present application is schematic and is only a logical functional grouping. In actual implementation, other grouping methods may be used.

[0178] Figure 10 shows a structural diagram of a communication device 1000, which can be used to perform the functions of the terminal device involved in the above embodiments. As an implementation method, the communication device 1000 shown in Figure 10 includes: a transceiver unit 1001, and a processing unit 1002;

[0179] The transceiver unit 1001 is configured to receive the SIB of the cell on the downlink carrier of the cell. For example, the transceiver unit 1001 may support the communication device 1000 to execute S603.

[0180] The processing unit 1002 is configured to send a random access request to access the cell on an uplink carrier of the cell according to the SIB, wherein the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier. For example, the processing unit 1002 can support the communication device 1000 to execute S604 to S605.

[0181] For the description of the uplink carrier of the cell, the downlink carrier of the cell, and the SIB of the cell, reference may be made to that in the above method embodiment.

[0182] Specifically, all relevant contents of each step involved in the method embodiment shown in FIG6 can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 1000 is used to perform the functions of the terminal device in the communication method shown in FIG6, and thus can achieve the same effect as the above-mentioned communication method.

[0183] FIG11 shows a structural diagram of a communication device 1100, which can be used to perform the functions of the access network device involved in the above embodiments. As an implementation method, the communication device 1100 shown in FIG11 includes: a transceiver unit 1101;

[0184] The transceiver unit 1101 is configured to send the SIB of the cell via the downlink carrier of the cell. For example, the transceiver unit 1101 may be configured to support the communication device 1100 in executing S601.

[0185] The transceiver unit 1101 is further configured to receive a random access request for accessing the cell on an uplink carrier of the cell, wherein the frequency band corresponding to the uplink carrier of the cell is different from the frequency band corresponding to the downlink carrier. For example, the transceiver unit 1101 may be configured to support the communication device 1100 in executing S605.

[0186] For the description of the uplink carrier of the cell, the downlink carrier of the cell, and the SIB of the cell, reference may be made to that in the above method embodiment.

[0187] Specifically, all relevant contents of each step involved in the method embodiment shown in FIG6 can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 1100 is used to perform the functions of the access network device in the communication method shown in FIG6, and thus can achieve the same effect as the above-mentioned communication method.

[0188] FIG12 shows a structural diagram of a communication device 1200, which can be used to perform the functions of the terminal device involved in the above embodiments. As an implementation method, the communication device 1200 shown in FIG12 includes: a transceiver unit 1201, a processing unit 1202;

[0189] The transceiver unit 1201 is configured to receive first indication information from an access network device corresponding to a first cell. For example, the transceiver unit 1201 may be configured to support the communication apparatus 1200 in executing S901.

[0190] The processing unit 1202 is configured to perform a cell handover according to the cell handover method indicated by the first indication information, wherein the first indication information is used to indicate a cell handover method in which an uplink carrier is switched but a downlink carrier is not switched. For example, the processing unit 1202 can be configured to support the communication device 1200 in executing S902.

[0191] For the description of the first indication information, please refer to the above method embodiment.

[0192] Specifically, all relevant contents of each step involved in the method embodiment shown in FIG9 can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 1200 is used to perform the functions of the terminal device in the communication method shown in FIG9, and thus can achieve the same effect as the above-mentioned communication method.

[0193] FIG13 shows a structural diagram of a communication device 1300, which can be used to perform the functions of the access network device involved in the above embodiments. As an implementation method, the communication device 1300 shown in FIG13 includes: a processing unit 1301, a transceiver unit 1302;

[0194] The processing unit 1301 is configured to obtain first indication information. For example, the processing unit 1301 may be configured to support the communication device 1300 in executing S901.

[0195] The transceiver unit 1302 is configured to send first indication information, wherein the first indication information is used to indicate a cell switching mode in which the uplink carrier is switched but the downlink carrier is not switched. For example, the transceiver unit 1302 can be configured to support the communication device 1300 in executing S901.

[0196] Among them, the relevant descriptions of the first indication information and the cell switching method can refer to those in the above method embodiment.

[0197] Specifically, all relevant contents of each step involved in the method embodiment shown in FIG9 can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 1300 is used to perform the functions of the access network device in the communication method shown in FIG9, and thus can achieve the same effect as the above-mentioned communication method.

[0198] As mentioned above, the processing module can be a processor or a controller. It can implement or execute the various exemplary logical blocks, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and so on. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 1000, communication device 1100, communication device 1200, and communication device 1300 involved in the embodiments of the present application can be the communication device 1400 shown in Figure 14. For example, the terminal equipment and access network equipment mentioned above can adopt the composition structure shown in Figure 14 or include the components shown in Figure 14. Figure 14 is a schematic diagram of the composition of a communication device 1400 provided in an embodiment of the present application. As shown in Figure 14, the communication device 1400 may include a processor 1401, a communication line 1402 and a communication interface 1403.

[0199] Furthermore, the communication device 1400 may further include a memory 1404 , wherein the processor 1401 , the memory 1404 and the communication interface 1403 may be connected via a communication line 1402 .

[0200] The processor 1401 may be a central processing unit (CPU), a general-purpose processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The processor 1401 may also be other communication devices with processing capabilities, such as circuits, devices, or software modules.

[0201] The communication line 1402 is used to transmit information between the various components included in the communication device 1400.

[0202] Communication interface 1403 is used to communicate with other devices or other communication networks. The other communication network can be Ethernet, a radio access network (RAN), a wireless local area network (WLAN), etc. Communication interface 1403 can be a radio frequency module, a transceiver, or any communication device capable of achieving communication. The embodiment of the present application is described using the communication interface 1403 as an example of a radio frequency module, wherein the radio frequency module may include an antenna, a radio frequency circuit, etc., and the radio frequency circuit may include a radio frequency integrated chip, a power amplifier, etc.

[0203] The memory 1404 is used to store instructions, where the instructions may be computer programs.

[0204] Among them, the memory 1404 can be a read-only memory (ROM) or other types of static storage devices that can store static information and / or instructions, or a random access memory (RAM) or other types of dynamic storage devices that can store information and / or instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage, magnetic disk storage media or other magnetic storage devices, and optical disc storage includes compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.

[0205] It should be noted that memory 1404 can exist independently of processor 1401 or can be integrated with processor 1401. Memory 1404 can be used to store instructions, program code, or some data. Memory 1404 can be located within or outside of communication device 1400, without limitation. Processor 1401 is configured to execute instructions stored in memory 1404 to implement the random access procedure preamble transmission method provided in the following embodiments of this application.

[0206] In one example, the processor 1401 may include one or more CPUs, such as CPU0 and CPU1 in FIG. 14 .

[0207] As an optional implementation, the communication device 1400 includes multiple processors. For example, in addition to the processor 1401 in FIG. 14 , it may also include a processor 1407 .

[0208] As an optional implementation, the communication device 1400 further includes an output device 1405 and an input device 1406. The input device 1406 is a keyboard, a mouse, a microphone, or a joystick, and the output device 1405 is a display screen, a speaker, or other devices.

[0209] It should be noted that the communication device 1400 may be a desktop computer, a portable computer, a network server, a mobile phone, a tablet computer, a wireless terminal device, an embedded device, a chip system, or a device having a structure similar to that shown in FIG14 . Furthermore, the component structure shown in FIG14 does not limit the communication device. In addition to the components shown in FIG14 , the communication device may include more or fewer components than shown, or combine certain components, or arrange the components differently.

[0210] In the embodiment of the present application, the chip system can be composed of chips, or can include chips and other discrete devices.

[0211] The embodiments of the present application also provide a computer-readable storage medium. All or part of the processes in the above-mentioned method embodiments can be completed by a computer program to instruct the relevant hardware. The program can be stored in the above-mentioned computer-readable storage medium. When the program is executed, it can include the processes of the above-mentioned method embodiments. The computer-readable storage medium can be a terminal device of any of the above-mentioned embodiments, such as: an internal storage unit including a data transmission end and / or a data receiving end, such as a hard disk or memory of the terminal device. The above-mentioned computer-readable storage medium can also be an external storage device of the above-mentioned terminal device, such as a plug-in hard disk, a smart memory card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the above-mentioned terminal device. Furthermore, the above-mentioned computer-readable storage medium can also include both the internal storage unit of the above-mentioned terminal device and an external storage device. The above-mentioned computer-readable storage medium is used to store the above-mentioned computer program and other programs and data required by the above-mentioned terminal device. The above-mentioned computer-readable storage medium can also be used to temporarily store data that has been output or is to be output.

[0212] It should be understood that the collection, storage, use, processing, transmission, provision, and disclosure of user personal information involved in the technical solution of this application complies with relevant laws and regulations and does not violate public order and good morals. For example, in the technical solution of this application, the processing of user personal information is carried out with the user's authorization, and the same description is not repeated here.

[0213] It should be noted that the terms "first" and "second" in the specification, claims, and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products, or devices.

[0214] It should be understood that in the present application, "at least one (item)" refers to one or more, "more than one" refers to two or more, "at least two (items)" refers to two or three and more than three, and "and / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0215] It should be understood that in the embodiments of the present application, "B corresponding to A" means that B is associated with A. For example, B can be determined based on A. It should also be understood that determining B based on A does not mean determining B based solely on A; B can also be determined based on A and / or other information. In addition, the "connection" in the embodiments of the present application refers to various connection methods, such as direct connection and indirect connection, to achieve communication between devices, and the embodiments of the present application do not impose any limitations on this.

[0216] Unless otherwise specified, the "transmission" (transmit / transmission) appearing in the embodiments of the present application refers to bidirectional transmission, including the actions of sending and / or receiving. Specifically, the "transmission" in the embodiments of the present application includes the sending of data, the receiving of data, or the sending of data and the receiving of data. In other words, the data transmission here includes uplink and / or downlink data transmission. Data may include channels and / or signals, uplink data transmission is uplink channel and / or uplink signal transmission, and downlink data transmission is downlink channel and / or downlink signal transmission. The "network" and "system" appearing in the embodiments of the present application express the same concept, and the communication system is the communication network.

[0217] Through the description of the above implementation methods, technical personnel in the relevant field can clearly understand that for the convenience and simplicity of description, only the grouping of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be grouped into different functional modules to complete all or part of the functions described above.

[0218] In the several embodiments provided in this application, it should be understood that the disclosed communication devices and methods can be implemented in other ways. For example, the communication device embodiments described above are merely illustrative. For example, the grouping of the modules or units is merely a logical functional grouping. In actual implementation, there may be other grouping methods, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0219] The units described as separate components may or may not be physically separate, and the components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0220] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0221] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for enabling a device, such as a single-chip microcomputer, a chip, etc., or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media for storing program codes, such as a USB flash drive, a mobile hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.

[0222] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A communication method, characterized in that: The method comprises: Receiving a system information block SIB of the cell on a downlink carrier of the cell; According to the SIB, a random access request for accessing the cell is sent on an uplink carrier of the cell, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier.

2. The method according to claim 1, characterized in that The SIB of the cell indicates that a frequency difference between a lowest frequency of a frequency band corresponding to the uplink carrier of the cell and a lowest frequency of a frequency band corresponding to the downlink carrier of the cell is greater than a threshold.

3. The method according to claim 1, characterized in that The SIB of the cell indicates an uplink and downlink frame ratio of time domain resources corresponding to the uplink carrier of the cell, and an uplink and downlink frame ratio of time domain resources corresponding to the downlink carrier of the cell.

4. The method according to claim 3, characterized in that An uplink and downlink frame ratio of time domain resources corresponding to the uplink carrier of the cell is different from an uplink and downlink frame ratio of time domain resources corresponding to the downlink carrier of the cell.

5. A communication method, characterized in that: The method comprises: Sending a system information block SIB of the cell on a downlink carrier of the cell; A random access request for accessing the cell is received on an uplink carrier of the cell, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier.

6. The method according to claim 5, characterized in that The SIB of the cell indicates that a frequency difference between a lowest frequency of a frequency band corresponding to the uplink carrier of the cell and a lowest frequency of a frequency band corresponding to the downlink carrier of the cell is greater than a threshold.

7. The method according to claim 5, characterized in that The SIB of the cell indicates an uplink and downlink frame ratio of time domain resources corresponding to the uplink carrier of the cell, and an uplink and downlink frame ratio of time domain resources corresponding to the downlink carrier of the cell.

8. The method according to claim 7, characterized in that: An uplink and downlink frame ratio of time domain resources corresponding to the uplink carrier of the cell is different from an uplink and downlink frame ratio of time domain resources corresponding to the downlink carrier of the cell.

9. A communication device, characterized in that: The communication device comprises: a transceiver unit, configured to receive a system information block (SIB) of the cell on a downlink carrier of the cell; The processing unit is configured to send a random access request for accessing the cell on an uplink carrier of the cell according to the SIB, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier.

10. A communication device, characterized in that: The communication device comprises: A transceiver unit, configured to send a system information block (SIB) of the cell via a downlink carrier of the cell; The transceiver unit is further configured to receive a random access request for accessing the cell on an uplink carrier of the cell, wherein a frequency band corresponding to the uplink carrier of the cell is different from a frequency band corresponding to the downlink carrier.

11. A communication device, characterized in that: The communication device includes a processor and a communication interface, and the processor and the communication interface are used to support the communication device to execute the communication method according to any one of claims 1 to 4, or to execute the communication method according to any one of claims 5 to 8.

12. A communication system, characterized in that: The communication system includes the communication device according to claim 9 and claim 10, or the communication system includes the communication device according to claim 9 and claim 11, or the communication system includes the communication device according to claim 10 or 11.

13. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, which, when executed on a computer, enable the computer to execute the method according to any one of claims 1 to 4, or enable the computer to execute the method according to any one of claims 5 to 8.

14. A computer program product, characterized in that The computer program product includes computer instructions, and when the computer instructions are run on a computer, the computer is caused to execute the method according to any one of claims 1 to 4, or the method according to any one of claims 5 to 8.

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