Patent Publication Number: US-2022232637-A1

Title: Random access method and device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 16/759,542 filed on Apr. 27, 2020, which is a national phase application of PCT Application No. PCT/CN2017/108285, filed on Oct. 30, 2017, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to the technical field of communications, and particularly to a random access method and device. 
     BACKGROUND 
     Over the past about 30 years, the mobile communications have evolved from a second-generation (2G) mobile communication network to a fifth-generation (5G) mobile communication network by leaps and bounds. In research discussions of the 5G project, supplementary uplink (SUL) is introduced in a cell to support uplink information of multiple terminal devices, thus enhancing an uplink coverage in the cell. 
     In related arts, if a cell that user equipment (UE) accesses is configured only with one uplink carrier and one downlink carrier, the UE can transmit a random access preamble through the uplink carrier to initiate a random access when performing the random access. However, if the cell that the UE accesses is configured with an SUL carrier, the cell includes two uplink carriers. i.e., one SUL carrier and one non-SUL carrier. In the latter case, the UE cannot determine on which uplink carrier to initiate a random access process when performing a random access. 
     SUMMARY 
     Random access methods, communication devices and computer-readable storage mediums are provided in embodiments of the disclosure. The technical solutions are described as below. 
     A first aspect according to the embodiments of the disclosure provides a random access method applied to a terminal. The method includes: receiving, by a terminal, a radio resource control (RRC) message sent by a base station, the RRC message comprising a power threshold; detecting, by the terminal, a reference signal received power (RSRP) of a current downlink carrier; determining, by the terminal, a first uplink carrier among a plurality of uplink carriers corresponding to the base station according to the RSRP and the power threshold; and transmitting, by the terminal, a random access preamble to the base station using the first uplink carrier. The plurality of uplink carriers comprise a supplementary uplink (SUL) carrier and a non-SUL carrier. 
     A second aspect according to the embodiments of the disclosure provides a random access method applied to a base station. The method includes: transmitting, by a base station, a radio resource control (RRC) message to a terminal, the RRC message comprising a power threshold; and receiving, by the base station, a random access preamble sent by the terminal using a first uplink carrier. The first uplink carrier is determined by the terminal among a plurality of uplink carriers corresponding to the base station according to a reference signal received power (RSRP) of a current downlink carrier and the power threshold. The plurality of uplink carriers comprise a supplementary uplink (SUL) carrier and a non-SUL carrier. 
     A third aspect according to the embodiments of the disclosure provides a terminal device, which includes a processor, and a memory configured to store instructions executable by the processor. The processor is configured to: receive a radio resource control (RRC) message sent by a base station, the RRC message comprising a power threshold; detect a reference signal received power (RSRP) of a current downlink carrier; determine a first uplink carrier among a plurality of uplink carriers corresponding to the base station according to the RSRP and the power threshold; and transmit a random access preamble to the base station using the first uplink carrier. The plurality of uplink carriers comprise a supplementary uplink (SUL) carrier and a non-SUL carrier. 
     A fourth aspect according to the embodiments of the disclosure provides a base station, which includes a processor and a memory configured to store instructions executable by the processor. The processor is configured to perform the method in the second aspect. 
     A fifth aspect according to the embodiments of the disclosure provides a non-transitory computer-readable storage medium having stored thereon instructions that, when executed by a processor of a terminal device, cause the terminal device to perform the method in the first aspect. 
     A sixth aspect according to the embodiments of the disclosure provides a non-transitory computer-readable storage medium having stored thereon instructions that, when executed by a processor of a base station, cause the base station to perform the method in the second aspect. 
     It should be understood that the general description above and the following detailed description in the disclosure are merely exemplary and explanatory and are not intended to limit the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure. 
         FIG. 1A  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1B  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1C  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1D  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1E  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1F  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1G  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1H  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1I  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 1J  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 2A  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 2B  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 2C  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 2D  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 2E  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 2F  is a flowchart illustrating a random access method according to an exemplary embodiment; 
         FIG. 3  is an interaction diagram illustrating a random access method according to an exemplary embodiment; 
         FIG. 4  is an interaction diagram illustrating a random access method according to an exemplary embodiment; 
         FIG. 5  is an interaction diagram illustrating a random access method according to an exemplary embodiment; 
         FIG. 6A  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6B  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6C  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6D  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6E  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6F  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6G  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6H  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6I  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6J  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6K  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6L  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6M  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6N  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6O  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6P  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 6Q  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7A  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7B  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7C  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7D  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7E  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7F  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7G  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7H  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7I  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 7J  is a structural schematic diagram illustrating a random access device according to an exemplary embodiment; 
         FIG. 8  is a structural block diagram illustrating a random access device according to an exemplary embodiment; and 
         FIG. 9  is a structural block diagram illustrating a random access device according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the present disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the present disclosure as recited in the appended claims. 
     The technical solutions provided by the embodiments of the disclosure relate to a terminal device and a base station that are connected to each other via a mobile communication network. The terminal can be a cell phone, a tablet, a smart watch and other device with functions of mobile communication, and there are no limits made in the embodiments of the disclosure. In related art, if a cell accessed by a terminal device is configured with an SUL carrier, the cell includes two uplink carriers, i.e., one SUL carrier and one non-SUL carrier. As a result, the terminal device cannot determine on which uplink carrier to initiate a random access process when the random access is performed. In the technical solutions provided by the embodiments of the disclosure, the terminal device can determine a first target uplink carrier used for transmitting a random access preamble among a plurality of uplink carriers corresponding to a target base station, and transmit a random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In the embodiments of the disclosure, a random access method is provided, and an execution subject of the method includes a terminal device and a base station. Two sets of embodiments are arranged in the disclosure depending on execution subjects of the methods, which are described as follows. 
     Terminal Device Side 
       FIG. 1A  is a flowchart illustrating a random access method according to an exemplary embodiment, herein the method is applied to the terminal device. As illustrated in  FIG. 1A , the method includes following operations  101  and  102 . 
     In operation  101 , a first target uplink carrier is determined among a plurality of uplink carriers corresponding to a target base station, the plurality of uplink carriers including at least one supplementary uplink (SUL) carrier. 
     Exemplarily, the plurality of uplink carriers corresponding to the target base station can include at least one SUL carrier and one non-SUL carrier, herein the non-SUL carrier is usually a carrier in a high frequency band and the SUL carrier is usually a carrier in a low frequency band. In the embodiments of the disclosure, a target base station will be described as an example, herein the target base station includes: two uplink carriers including one SUL carrier and one non-SUL carrier, and a downlink carrier paired with the two uplink carriers. 
     The target base station performs system broadcasting according to a preset time interval. herein a system broadcasting message can include a carrier identifier of the SUL carrier, a carrier identifier of a non-SUL carrier and a carrier identifier of a downlink carrier. If an uplink carrier paired with the downlink carrier is pre-agreed between the terminal device and the target base station agree, the system broadcasting message can merely include the carrier identifier of the SUL carrier and the carrier identifier of the downlink carrier. In this case, the terminal device can obtain the carrier identifier of another non-SUL carrier paired with the downlink carrier according to the agreement after receiving the system broadcasting message. Or, if a downlink carrier paired with the uplink carrier is pre-agreed between the terminal device and the target base station, the system broadcasting message can merely include the carrier identifier of the SUL carrier and the carrier identifier of the non-SUL carrier. In this case, the terminal device can obtain the carrier identifier of the downlink carrier paired with the non-SUL carrier according to the agreement after receiving the system broadcasting message. The carrier identifier can be an identity (ID) of the carrier pre-agreed between the terminal and the target base station; or if the frequencies of the two uplink carriers and the downlink carrier are different from each other, the carrier identifier can also be the frequency of each carrier. There are no limits made in the embodiments of the disclosure. 
     According to an embodiment of the disclosure, the terminal device can monitor the system broadcasting message of the target base station and access the target base station according to the system broadcasting message. During an interaction process between the terminal device and the target base station, the target base station usually configures a physical uplink control channel (PUCCH) on an uplink carrier with a better signal quality to ensure a good communication quality of the PUCCH, namely the reliability in transmission of a control signaling, thus the terminal can determine, as a first target uplink carrier, a carrier configured with the PUCCH among the plurality of uplink carriers corresponding to the target base station and transmit a random access preamble using the determined carrier, thereby improving the reliability in transmission of the random access preamble. For example, if the target base station configures the PUCCH on the SUL carrier, the terminal device can determine the SUL carrier as the first target uplink carrier; if the target base station configures the PUCCH on the non-SUL carrier, the terminal can determine the non-SUL carrier as the first target uplink carrier; if the target base station configures that the PUCCH can be dynamically regulated on the SUL carrier and the non-SUL carrier, then based on a time when the random access is initiated, the terminal device can also determine, as the first target uplink carrier, the SUL carrier or the non-SUL carrier which is configured with the PUCCH at the time when the random access is initiated. 
     According to an embodiment of the disclosure, the terminal device can also obtain a random access resource included by each of the plurality of uplink carriers respectively and determine the first target uplink carrier according to the random access resource included by each uplink carrier. For example, the terminal device can obtain the random access resources included by the SUL carrier and the non-SUL carrier respectively, and then obtain, a carrier where the earliest-arriving random access resource is on, as the first target uplink carrier according to the time when the random access is initiated, herein the earliest-arriving random access resource is a resource that arrives at a time closest to the time when the random access is initiated. 
     In operation  102 , the random access preamble is transmitted to the target base station using the first target uplink carrier. 
     Exemplarily, after the first target uplink carrier for transmitting the random access preamble is determined among the plurality of uplink carriers, the terminal device can transmit the random access preamble to the target base station using the first target uplink carrier. Specifically, the terminal device can transmit the random access preamble using a preset first transmitting power and wait to receive random access response information from the target base station. if the random access response information is not received from the target base station in a second preset period, the terminal device can continue to transmit the random access preamble on the first target uplink carrier using a preset second transmitting power and re-initiate the random access. Or, the terminal device can determine a second target uplink carrier, other than the first target uplink carrier, among the plurality of uplink carriers, and transmit the random access preamble using the second target uplink carrier. 
     In the technical solutions provided by the embodiments of the disclosure, a terminal device can determine a first target uplink carrier used for transmitting a random access preamble among a plurality of uplink carriers corresponding to a target base station, and transmit a random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in  FIG. 1B , determining a first target uplink carrier among a plurality of uplink carriers corresponding to a target base station can be implemented by operations  1011  and  1012 . 
     In operation  1011 , a carrier identifier of the first target uplink carrier is received from a base station. 
     In operation  1012 , the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the carrier identifier of the first target uplink carrier. 
     Exemplarily, when determining that the terminal device needs to initiate a random access, the target base station can determine the first target uplink carrier configured for the terminal device to transmit the random access preamble among the plurality of uplink carriers corresponding to the target base station and transmit the carrier identifier of the first target uplink carrier to the terminal device. After receiving the carrier identifier of the first target uplink carrier from the target base station, the terminal device can obtain, as the first target uplink carrier, an uplink carrier with a carrier identifier same as the carrier identifier of the first target uplink carrier, among the plurality of uplink carrier. 
     The carrier identifier of the first target uplink carrier can be: a carrier name of the first target uplink carrier, i.e., an SUL carrier or a non-SUL carrier; or an ID of the first target uplink carrier pre-agreed between the terminal device and the target base station; or a carrier index number, i.e., the index number of each uplink carrier pre-agreed between the terminal and the base station, when the target base station transmit the carrier identifier of the first target uplink carrier, it can directly transmit the index number of the first target uplink carrier. If frequencies of the plurality of uplink carriers corresponding to the target base station are different from each other, the carrier identifier of the first target uplink carrier can also be a carrier frequency of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 1C , the operation  1011  of receiving a carrier identifier of the first target uplink carrier can be implemented by operation  1011   a.    
     In operation  1011   a , an RRC message including the carrier identifier of the first target uplink carrier is received from a target base station. 
     Exemplarily, the RRC message is information transmitted by the target base station to regulate and control resource configuration. After the terminal device accesses the target base station, before configuring other uplink resource or other downlink resource for the terminal device using the RRC message, the target base station can configure a carrier used for initiating a random access for the terminal device in advance, thereby avoiding a failure in a random access caused by a situation that the terminal device cannot determine a carrier used to upload the random access preamble when initiating the random access. 
     With two uplink carriers, i.e., one SUL carrier and one non-SUL carrier, included by the target base station as an example, the target base station can determine random access resources included by the SUL carrier and the non-SUL carrier first, and then determine, according to the random access resources included by the SUL carrier and the non-SUL carrier, the first target uplink carrier configured for the terminal device to initiate the random access, and notify the terminal device of the carrier identifier of the first target uplink carrier by including the carrier identifier of the first target uplink carrier in the RRC message transmitted to the terminal device. After receiving the RRC message, the terminal device can obtain a first carrier identifier included in the RRC message and determine, as the first target uplink carrier, a carrier with a carrier identifier same as the first carrier identifier among the SUL carrier and the non-SUL carrier. In the embodiments of the disclosure, the carrier identifier of the first target uplink carrier, which is included in the RRC message, is designated as the first carrier identifier for the purpose of easy differentiation. 
     Specifically, a first function field can be added in the RRC message in advance and pre-agreed between two sides: the terminal device and the target base station. After obtaining the first target uplink carrier, the target base station can write the first function field in the carrier identifier of the first target uplink carrier. After receiving the RRC message, the terminal device can parse the first function field to obtain the first carrier identifier and determine, as the first target uplink carrier, a carrier that is in the SUL carrier and the non-SUL carrier included by the target base station and corresponds to the first carrier identifier. 
     In the technical solutions provided in the embodiments of the disclosure, the terminal device can determine, according to the configuration of the target base station, the first target uplink carrier used for transmitting the random access preamble among the plurality of uplink carriers corresponding to the target base station, and transmit the random access preamble to the target base station using the first target uplink carrier to initiate the random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in  FIG. 1D , the operation  1011  of receiving a carrier identifier of a first target uplink carrier from the base station can be implemented by operation  1011   b.    
     In operation  1011   b , allocation information of a random access preamble is received from the target base station, the allocation information of the random access preamble including the carrier identifier of the first target uplink carrier. 
     Exemplarily, the random access includes a competitive random access and a non-competitive random access. When triggering the non-competitive random access using a physical downlink control channel (PDCCH) command, the target base station can allocate the random access preamble to the terminal device according to a preset rule, and obtain, a carrier where the PDCCH is on among a plurality of uplink carriers, as the first target uplink carrier configured for the terminal device to transmit the random access preamble; the target base station can then generate the allocation information of the random access preamble according to the random access preamble and the carrier identifier of the first target uplink carrier, and transmit the allocation information of the random access preamble to the terminal device. In the embodiments of the disclosure, the carrier identifier of the first target uplink carrier, which is included in the allocation information of the random access preamble, is designated as a second carrier identifier for the purpose of easy differentiation. 
     After receiving the allocation information of the random access preamble, the terminal device can obtain the second carrier identifier included by the allocation information of the random access preamble, and obtain a carrier with a carrier identifier same as the second carrier identifier among the plurality of uplink carriers corresponding to the target base station, and the carrier is then first target uplink carrier configured for the terminal device to transmit the random access preamble by the target base station. At this time, the terminal device can initiate the random access using the first target uplink carrier to transmit the random access preamble allocated by the target base station to the terminal device. 
     In a practical application, a function field can be added in the allocation information of the random access preamble to carry the carrier identifier of the first target uplink carrier. 
     In the technical solutions provided in the embodiments of the disclosure, the terminal device can determine, according to an advance configuration of the target base station, the first target uplink carrier used for transmitting the random access preamble among the plurality of uplink carriers corresponding to the target base station, and transmit the random access preamble to the target base station using the first target uplink carrier to initiate the random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in  FIG. 1E , the operation  1011  of receiving a carrier identifier of a first target uplink carrier transmitted by a base station can be implemented by operation  1011   c.    
     In operation  1011   c , handover command information is received from an original base station when the terminal device performs handover between the original base station and the target base station, the handover command information including the carrier identifier of the first target uplink carrier. 
     Exemplarily, two uplink carriers, i.e., an SUL carrier and a non-SUL carrier, included by the target base station will be described as an example. When being used, the terminal device may perform the handover to the target base station. When detecting that the terminal device needs to perform the handover to the target base station, the original base station which the terminal device accesses currently can transmit a handover request to the target base station which the terminal device is about to access; after receiving the handover request, the target base station can obtain, a carrier where the PDCCH is on among the SUL carrier and the non-SUL carrier, as the first target uplink carrier configured for the terminal device to transmit the random access preamble, generate handover request response information according to the carrier identifier of first target uplink carrier, and transmit the handover request response information to the original base station. In a practical application, the handover request response information can also include the carrier identifier of the SUL carrier and carrier identifier of the non-SUL carrier. The original base station can generate, according to the handover request response information, the handover command information including the carrier identifier of the SUL carrier, the carrier identifier of the non-SUL carrier and the carrier identifier of the first target uplink carrier, and transmit the handover command information to the terminal device. In the embodiments of the disclosure, the carrier identifier of the first target uplink carrier, which is included in the handover command information, is designated as a third carrier identifier for the purpose of differentiation. 
     After receiving the handover command information from the original base station, the terminal device obtains, a carrier with a carrier identifier same as the third carrier identifier among the SUL carrier and the non-SUL carrier, as a carrier for transmitting the random access preamble, herein the carrier is the first target uplink carrier configured for the terminal device by the target base station. 
     Specifically, a fourth function field can be set in the handover request response information in advance and pre-agreed between two sides: the original base station and the target base station. The target base station can write the carrier identifier of the first target uplink carrier into the fourth function field and the original base station can obtain the carrier identifier of the first target uplink carrier by parsing information in the fourth function field after receiving the handover request response information. In the same way, a fifth function field can be configured in the handover command information and is located in mobility control information of the handover command information and pre-agreed between the two sides: the original base station and the terminal device. The original base station can write the carrier identifier of the first target uplink carrier into the fifth function field and after receiving the handover command information, the terminal device can obtain a fourth carrier identifier by parsing information of the fifth function field and the fourth carrier identifier can be carrier identifier of the first target uplink carrier configured for the terminal device by the target base station. 
     In the technical solutions provided in the embodiments of the disclosure, when being able to performing handover to the target base station, the terminal device can determine, according to an advance configuration of the target base station, the first target uplink carrier used for transmitting the random access preamble among the plurality of uplink carriers corresponding to the target base station, and transmit the random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in FIG. the operation  1011  of receiving a carrier identifier of a first target uplink carrier from the base station can be implemented by operation  1011   d.    
     In operation  1011   d , a reconfiguration message is received from the target base station after the target base station re-establishes a secondary cell group (SCG) or modifies the SCG, the reconfiguration message including the carrier identifier of the first target uplink carrier. 
     Exemplarily, the target base station may re-establish or modify the SCG in the cells and may reconfigure a carrier used for transmitting a random access preamble for a terminal device after re-establishing or modifying the SCG because different SCGs maintain different resources. According to an embodiment of the disclosure, after re-establishing or modifying the SCG, the target base station obtains, among a plurality of uplink carriers, a carrier where a current PDCCH is on, as the first target uplink carrier configured for the terminal device to transmit the random access preamble. Because after the target base station re-establishes or modifies the SCG, it needs to transmit a reconfiguration message to the terminal device and notifies the terminal device of a latest resource configuration situation so that the carrier identifier of the first target uplink carrier can be carried in the reconfiguration message to be transmitted to the terminal device. In the embodiments of the disclosure, the carrier identifier of the first target uplink carrier, which is included in the reconfiguration message, is designated as a fourth carrier identifier for the purpose of differentiation. 
     After receiving the reconfiguration message, the terminal device can obtain the fourth carrier identifier included in the reconfiguration message, and obtain, a carrier with a carrier identifier same as the fourth carrier identifier among the plurality of uplink carriers, as a carrier for transmitting the random access preamble, herein the carrier is the first target uplink carrier configured for the terminal device by the target base station. 
     Specifically, a sixth function field can be set in the reconfiguration message and is located in the SCG of mobility control information and pre-agreed between the two sides: the terminal device and the target base station. When transmitting the reconfiguration message, the target base station can write the carrier identifier of the first target uplink carrier into the sixth function field and after receiving the reconfiguration message, the terminal device can obtain the fourth carrier identifier by parsing information of the sixth function field and then the fourth carrier identifier is the carrier identifier of the first target uplink carrier. 
     In the technical solutions provided in the embodiments of the disclosure, after the target base station re-establishes or modifies the SCG, the terminal device can determine, according to an advance configuration of the target base station, the first target uplink carrier used for transmitting the random access preamble among the plurality of uplink carriers corresponding to the target base station, and transmit the random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in  FIG. 1G , the operation  101  of determining a first target uplink carrier among a plurality of uplink carriers corresponding to a target base station can be implemented by operations  1013  to  1015 . 
     In operation  1013 , an RRC message including a power threshold is received from the target base station. 
     In operation  1014 , a reference signal receiving power (RSRP) of a current downlink carrier is detected. 
     In operation  1015 , the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold. 
     The target base station includes a plurality of uplink carriers and one downlink carrier. During initialization, the target base station can test a value of an attenuation limit of the downlink carrier corresponding to each uplink carrier when a location of the terminal device remains unchanged. With a reference uplink carrier as an example, when a current location of the terminal device remains unchanged, the target base station can test a relationship between an attenuation degree of the downlink carrier and an attenuation degree of the reference uplink carrier, and determine the value of the attenuation limit of the downlink carrier corresponding to the reference uplink carrier. If the attenuation of the downlink carrier is greater than the value of the attenuation limit, the attenuation of the reference uplink carrier is excessively great and information is not able to be transmitted to the target base station effectively; if the attenuation of the downlink carrier is less than or equal to the value of the attenuation limit, the attenuation of the reference uplink carrier is small and reliability of uplink information can be ensured. The reference uplink carrier is any one of the plurality of uplink carriers. 
     The target base station can divide cells it covers into several regions, determine the value of the attenuation limit of the downlink carrier corresponding to each uplink carrier when the terminal device is in different regions and store the value of the attenuation limit of the downlink carrier corresponding to each uplink carrier according to each region. After the terminal device accesses the target base station, the target base station can obtain the value of the attenuation limit of the downlink carrier corresponding to each uplink carrier in the region where the terminal device is located, determine the power threshold according to the value of the attenuation limit and notifies the terminal device of the power threshold by an RRC message, so that the terminal device can determine, in the region, the first target uplink carrier according to the power threshold and the RSRP of the current downlink carrier. 
     With two uplink carriers, i.e., one SUL carrier and one non-SUL, included by the target base station as an example, it is assumed that in a current region where the terminal device is located, the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier is 30 dB and the value of the attenuation limit of the downlink carrier corresponding to the SUL carrier is 50 dB. That is to say, when the attenuation of the downlink carrier is 50 dB, the SUL carrier can still ensure reliable data transmission, whereas when the attenuation of the downlink carrier is greater than 30 dB, the non-SUL carrier cannot ensure the reliability of uplink data. As a result, the target base station can set the power threshold of the terminal device in the current region as 70 dB according to the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier, which means that when the RSRP of the received downlink carrier is less than 70 dB, the attenuation of the downlink carrier is greater than 30 dB and when the RSRP of the received downlink carrier is greater than or equal to 70 dB, the attenuation of the downlink carrier is less than or equal to 30 dB. Then the target base station can notify the terminal device by the RRC message. The terminal device stores the power threshold, and when the random access is needed to be initiated, the terminal device first detects the RSRP of the current downlink carrier, which shows the attenuation degree of the downlink carrier, and then determines a value relationship between the RSRP and the power threshold. Specifically, the non-SUL carrier is determined as the first target uplink carrier when the RSRP is greater than or equal to the power threshold, i.e., the RSRP is greater than or equal to 70 dB; the SUL carrier is determined as the first target uplink carrier when the RSRP is less than the power threshold, i.e., the RSRP is less than 70 dB. 
     Specifically, a second function field can be added in the RRC message in advance and pre-agreed between the two sides: the terminal device and the target base station. After obtaining the power threshold, the target base station can write the power threshold into the second function field. The terminal device can obtain the power threshold by parsing the second function field after receiving the RRC message. 
     In the technical solutions provided in the embodiments of the disclosure, the terminal device can determine, according to a receiving power of a reference signal of the downlink carrier and the power threshold configured in advance by the target base station, the first target uplink carrier for transmitting a random access preamble among the plurality of uplink carriers corresponding to the target base station, and transmit the random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 1H , the operation  101  of determining a first target uplink carrier among a plurality of uplink carriers corresponding to a target base station can be implemented by operations  1016  to  1018 . 
     In operation  1016 , an RRC message including a quality threshold is received from the target base station. 
     In operation  1017 , a reference signal receiving quality (RSRQ) of a current downlink carrier is detected. 
     In operation  1018 , the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the RSRQ and the quality threshold. 
     The target base station includes a plurality of uplink carriers and one downlink carrier. During initialization, the target base station can test a value of a quality limit of the downlink carrier corresponding to each uplink carrier when a location of the terminal device remains unchanged. With a reference uplink carrier as an example, when a current location of the terminal device remains unchanged, the target base station can test a relationship between the RSRQ of the downlink carrier and the RSRQ of the reference uplink carrier and determine the value of the quality limit of the downlink carrier. If the RSRQ of the downlink carrier is greater than or equal to the value of the quality limit, it means the reference uplink carrier has a better quality at this time and reliability of uplink information can be ensured; if the RSRQ of the downlink carrier is less than the value of the quality limit, it means the reference uplink carrier has a worse quality at this time and the information may not be transmitted to the target base station effectively. The reference uplink carrier is any one of the plurality of uplink carriers. 
     The target base station can divide cells it covers into several regions, determine the value of the quality limit of the downlink carrier corresponding to each uplink carrier when the terminal device is in different regions and store the value of the quality limit of the downlink carrier corresponding to each uplink carrier according to each region. After the terminal device accesses the target base station, the target base station can obtain the value of the quality limit of the downlink carrier corresponding to each uplink carrier in the region where the terminal device is located, determine the quality threshold according to the value of the quality limit and notifies the terminal device by an RRC message so that the terminal device can determine, in the region, the first target uplink carrier according to the quality threshold and the RSRQ of the current downlink carrier. 
     With two uplink carriers, i.e., one SUL carrier and one non-SUL, included by the target base station as an example, suppose the terminal device is in a current region, and the value of the quality limit of the downlink carrier corresponding to the SUL carrier is −10 and the value of the quality limit of the downlink carrier corresponding to the non-SUL carrier is −5, then it means when downlink carrier has a worse quality, the SUL carrier can still ensure reliable data transmission and while the RSRQ of the downlink carrier is less than −5, the non-SUL carrier cannot ensure the reliability of uplink data. As a result, the target base station can set the quality threshold of the terminal device in the current region as −5 according to the value of the quality limit of the uplink carrier according to the non-SUL carrier and notify the terminal device by the RRC message. The terminal device stores the quality threshold and when the random access is needed to be initiated, the terminal device first detects the RSRQ of the current downlink carrier, and then determine a value relationship between the RSRQ and the quality threshold. The non-SUL carrier is determined as the first target uplink carrier when the RSRQ is greater than or equal to the quality threshold, which means the RSRQ is greater than or equal to −5; the SUL carrier is determined as the first target uplink carrier when the RSRQ is less than the quality threshold, which means the RSRQ of the downlink carrier is less than −5. 
     Specifically, a third function field can be added in the RRC message in advance and pre-agreed between two sides: the terminal device and the target base station. After obtaining the quality threshold, the target base station can write the quality threshold into the third function threshold and after receiving the RRC message, the terminal device can obtain the quality threshold by parsing the third function field. 
     In a practical application, the target base station can add the power threshold and the quality threshold in the RRC message at the same time and transmit the RRC message to the terminal device. After receiving the RRC message, the terminal device stores the power threshold and the quality threshold. When a random access is needed, the terminal device can first detect the RSRP and the RSRQ of the current downlink carrier and then determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold as well as the RSRQ and the quality threshold. For example, the terminal device can determine the value relationship between the RSRP of the downlink carrier and the power threshold and the value relationship between the RSRQ and the quality threshold respectively. The non-SUL carrier is determined as the first target uplink carrier in response to the RSRP being greater than or equal to the power threshold or in response to the RSRQ being greater than or equal to the quality threshold; and the SUL carrier is determined as the first target uplink carrier in response to the RSRP being less than the power threshold and the RSRQ being less than the quality threshold. 
     With two uplink carriers, i.e., one SUL carrier and one non-SUL, included by the target base station as an example, suppose the terminal device is in the current region, and the power threshold is set by the target base station as 70 dB and quality threshold is set as −5. When the random access is needed, the terminal device can first detect the RSRP and the RSRQ of the downlink carrier. The non-SUL carrier is determined as the first target uplink carrier when the RSRP is greater than or equal to 70 dB or the RSRQ is greater than or equal to −5 and the SUL carrier is determined as the first target uplink carrier when the RSRP is less than 70 dB or the RSRQ is less than −5. 
     In the technical solutions provided in the embodiments of the disclosure, the terminal device can determine, according to a receiving quality of a reference signal of the downlink carrier and the quality threshold set in advance by the target base station, the first target uplink carrier for transmitting a random access preamble among the plurality of uplink carriers corresponding to the target base station, and transmit the random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in  FIG. 1I , the method also includes operations  103  to  105 . 
     In operation  103 , random access response information is received from a target base station, the random access response information including a carrier identifier of a second target uplink carrier. 
     In operation  104 , the second target uplink carrier is determined among a plurality of uplink carriers corresponding to the target base station according to the carrier identifier of the second target uplink carrier. 
     In operation  105 , scheduling transmission information is transmitted to the target base station using the second target uplink carrier. 
     Exemplarily, after receiving a random access preamble from the terminal device, the target base station can transmit random access response information to the terminal device. If a current random access is a non-competitive random access, the terminal device can implement the random access according to the random access response information; if the current random access is a competitive random access, the terminal device needs to transmit the scheduled transmission information to the target base station according to the random access response information and at this time the target base station can also configure, for the terminal device, the second target uplink carrier used for transmitting the scheduled transmission information. 
     According to an embodiment of the disclosure, during the competitive random access, the target base station receives a random access preamble from the terminal device and can obtain a carrier, where a PDCCH is, from the plurality of uplink carriers corresponding to the target base station and determine the carrier the second target uplink carrier used by the terminal device to transmit the scheduled transmission information and carry the carrier identifier of the second target uplink carrier in the random access response information and transmit the random access response information to the terminal. In the embodiments of the disclosure, the carrier identifier of the second target uplink carrier, which is included in the random access response information, is designated as a fifth carrier identifier for the purpose of differentiation. After obtaining the random access response information, the terminal device obtains, a carrier with a carrier identifier same as the fifth carrier identifier among the plurality of uplink carriers, as a carrier for transmitting the scheduled transmission information, herein the carrier is the second target uplink carrier configured for the terminal device by the target base station. In a practical application, the second target uplink carrier can be same as or different from the first target uplink carrier. There are no limits made in the embodiments of the disclosure. 
     In the technical solutions provided in the embodiments of the disclosure, the terminal device can determine, according to configuration of the target base station, the second target uplink carrier for transmitting the scheduled transmission information among the plurality of uplink carriers, and transmit the scheduled transmission information to the target base station using the second target uplink carrier, so that the random access based on a competitive mechanism is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 1J , the method also includes operations  106  and  107 . 
     In operation  106 , a third target uplink carrier is determined among a plurality of uplink carriers corresponding to a target base station if random access response information is not received from the target base station in a second preset period. 
     In operation  107 , a random access preamble is transmitted to the target base station using the third target uplink carrier. 
     Exemplarily, if the terminal device does not receive the random access response information from the target base station in the second preset period after transmitting a random access preamble to the target base station, it means that the random access is unsuccessful and the terminal device can change the carrier for transmitting random access preamble. With two uplink carriers, i.e., one SUL carrier and one non-SUL, included by the target base station as an example, suppose a first target uplink carrier determined by the terminal device to transmit the random access preamble for the first time is the SUL carrier, if the random access response information is not received from the target base station in the second preset period, then terminal device can re-transmit the random access preamble to the target base station using the non-SUL carrier which is the third target uplink carrier. 
     According to an embodiment of the disclosure, if the terminal device transmits the random access preamble to the target base station on the first target uplink carrier with a first transmitting power, then the terminal device can continue to transmit the random access preamble to the target base station on the third target uplink carrier with the first transmitting power, which decreases losses of the terminal devices. 
     In the technical solutions provided in the embodiments of the disclosure, when the initiated random access is not responded, the terminal device can change the third target uplink carrier for transmitting the random access preamble, and re-transmit the random access preamble to the target base station using the third target uplink carrier, so that the success rate of the random access is increased. 
     Base Station Side 
     In the embodiments of disclosure, a random access method is provided and used in the base station which can transmit indication information to the terminal device and the indication information is configured to indicate a first target uplink carrier to be determined, by the terminal device for transmitting a random access preamble, among a plurality of uplink carriers corresponding to the base station, and the plurality of uplink carriers include at least one SUL carrier. 
     Exemplarily, the indication information can be a carrier identifier of a first target uplink carrier configured, by the base station, for the terminal device to transmit a random access preamble, and can also be a power threshold or a quality threshold configured, by the base station, for the terminal device. 
     With two uplink carriers, i.e., one SUL carrier and one non-SUL, included by the base station as an example, the base station can test a value of an attenuation limit according to the SUL carrier and a value of an attenuation limit according to the non-SUL carrier respectively when a location of the terminal device remains unchanged. With the non-SUL carrier as an example, when a current location of the terminal device remains unchanged, the base station can test a relationship between an attenuation degree of the downlink carrier and an attenuation degree of the non-SUL carrier and determine the value of the attenuation limit of the downlink carrier. If the attenuation of the downlink carrier is greater than the value of the attenuation limit, then the attenuation of the non-SUL carrier is excessively great and information is not able to be transmitted to the base station in an effective way; if the attenuation of the downlink carrier is less than or equal to the value of the attenuation limit, then attenuation of the non-SUL carrier at this time is smaller and reliability of uplink information can be ensured. In the same way, the value of the attenuation limit of the downlink carrier corresponding to the SUL carrier can be determined. 
     The base station can divide cells it covers into several regions, determine the value of the attenuation limit of the downlink carrier corresponding to the SUL carrier and the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier respectively when the terminal device is in different regions and store the value of the attenuation limit of the downlink carrier corresponding to the SUL carrier and the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier according to each region. After the terminal device accesses the base station, the base station can obtain, according to the region where the current terminal device is, the value of the attenuation limit of the downlink carrier corresponding to the SUL carrier and the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier, determine a power threshold according to the value of the attenuation limit and notifies the terminal device by an RRC message so that the terminal device in the region can determine the first target uplink carrier according to the power threshold and an RSRP of a current downlink carrier. 
     It is assumed that in a current region where the terminal device is located, the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier is 30 dB, and the value of the attenuation limit of the downlink carrier corresponding to the SUL carrier is 50 dB. That is to say, when the attenuation of the downlink carrier is 50 dB, the SUL carrier can still ensure reliable data transmission and when the attenuation of the downlink carrier is greater than 30 dB, the non-SUL carrier cannot ensure reliability of uplink data. As a result, the base station can set, according to the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier, the power threshold of the terminal device in the current region to 70 dB, which means that when the RSRP of the received downlink carrier is less than 70 dB, the attenuation of the downlink carrier is greater than 30 dB; when the RSRP of the received downlink carrier is greater than or equal to 70 dB, the attenuation of the downlink carrier is less than or equal to 30 dB. Then the base station can notify the terminal device of the power threshold by the RRC message. The terminal device stores the power threshold, and when the random access is needed to be initiated, the terminal device first detects the RSRP of the current downlink carrier, which shows the attenuation degree of the downlink carrier, and then determines a value relationship between the RSRP and the power threshold. Specifically, the non-SUL carrier is determined as the first target uplink carrier when the RSRP is greater than or equal to the power threshold, i.e., the RSRP is greater than or equal to 70 dB; the SUL carrier is determined as the first target uplink carrier when the RSRP is less than the power threshold, i.e., the RSRP is less than 70 dB. 
     According to an embodiment of the disclosure, the base station can test a value of quality limit of the downlink carrier corresponding to the SUL carrier and a value of quality limit of the downlink carrier corresponding to the non-SUL carrier respectively when the location of the terminal device remains unchanged. With the non-SUL carrier as an example, the base station can test the relationship between an RSRQ of the downlink carrier and an RSRQ of the non-SUL carrier and determine the value of the quality limit of the downlink carrier when the location of the terminal device remains unchanged. If the RSRQ of the downlink carrier is greater than or equal to the value of the quality limit, it means that the non-SUL carrier has a better quality and the reliability of the uplink information can be ensured; if the RSRQ of the downlink carrier is less than the value of the quality limit, it means that non-SUL carrier has a worse quality and the information may not be able to be transmitted to the base station. In the same way, the value of the quality limit of the downlink carrier according to the SUL carrier can be tested. 
     The base station can divide cells it covers into several regions, determine the value of the quality limit of the downlink carrier corresponding to the SUL carrier and the value of the quality limit of the downlink carrier corresponding to the non-SUL carrier respectively when the terminal device is in different regions and store the value of the quality limit of the downlink carrier corresponding to the SUL carrier and the value of the quality limit of the downlink carrier corresponding to the non-SUL carrier according to each region. After the terminal device accesses the base station, the base station can obtain, according to the region where the current terminal device is, the value of the quality limit of the downlink carrier corresponding to the SUL carrier and the value of the quality limit of the downlink carrier corresponding to the non-SUL carrier, determine a quality threshold according to the value of the quality limit and notifies the terminal device by the RRC message so that the terminal device in the region can determine the first target uplink carrier according to the quality threshold and an RSRQ of the current downlink carrier. 
     It is assumed that in the current region where the terminal device is located, the value of the quality limit of the downlink carrier corresponding to the SUL carrier is - 10 , and the value of the attenuation limit of the downlink carrier corresponding to the non-SUL carrier is −5. That is to say, when the downlink carrier has a worse quality, the SUL carrier can still ensure the reliable data transmission and when RSRQ of the downlink carrier is less than −5, the non-SUL carrier cannot ensure the reliability of uplink data. As a result the base station can set, according to the value of the quality limit corresponding to the non-SUL carrier, the quality threshold of the terminal device in the current region to −5 and notify the terminal device of the quality threshold by the RRC message. The terminal device stores the quality threshold and when the random access is needed to be initiated, the terminal device first detects the RSRQ of the current downlink carrier, and then determine a value relationship between the RSRQ and the quality threshold. The non-SUL carrier is determined as the first target uplink carrier when the RSRQ is greater than or equal to the quality threshold, which means the RSRQ is greater than or equal to −5; the SUL carrier is determined as the first target uplink carrier when the RSRQ is less than the quality threshold, which means the RSRQ of the downlink carrier is less than −5. 
     In an embodiment of the disclosure, as illustrated in  FIG. 2A , the random access method includes the operations  201  to  202 : 
     In operation  201 , a first target uplink carrier configured for a terminal device to transmit a random access preamble is obtained among a plurality of uplink carriers. 
     Exemplarily, a base station can determine a carrier, where a PUCCH is, as the first target uplink carrier configured for the terminal device to transmit the random access preamble. If the base station configures the PUCCH on an SUL carrier, the SUL carrier can be configured as the first target uplink carrier, and the terminal device can transmit the random access preamble to the base station using the SUL carrier; if the base station configures the PUCCH on an non-SUL carrier, the non-SUL carrier can be configured as the first target uplink carrier, and the terminal device can transmit the random access preamble to the base station using the non-SUL carrier; if the base station configures that the PUCCH can be regulated dynamically on both the SUL carrier and the non-SUL carrier, then based on a time when a random access is initiated, the base station can determine, as the first target uplink carrier, the SUL carrier or the non-SUL carrier where the PUCCH is on at the time when the random access is initiated. 
     Alternatively, the base station can obtain a random access resource included by the SUL carrier and a random access resource included by the non-SUL carrier respectively, and determine the first target uplink carrier according to the random access resource included by the SUL carrier and the random access resource included by the non-SUL carrier. For example, according to a time when the random access is initiated, the terminal device can obtain a carrier where an earliest-arriving random access resource is on, and configure the obtained carrier as the first target uplink carrier, herein the earliest-arriving random access resource is a random access resource that arrives at a time closest to the time when the random access is initiated. 
     Alternatively, the base station can also evaluate a signal quality of the SUL carrier and a signal quality of the non-SUL carrier in advance, select a carrier with a better signal quality and configure the selected carrier as the first target uplink carrier. Specifically, the base station can evaluate the signal quality of the SUL carrier and the signal quality of the non-SUL carrier according to a number of lost packets in a preset reference period. The less the packets are lost, the better the signal quality is. 
     In operation  202 , a carrier identifier of the first target uplink carrier is transmitted to the terminal device to enable the terminal device to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the base station according to the carrier identifier of the first target uplink carrier. 
     Exemplarily, after determining the first target uplink carrier needed to be configured for the terminal device, the base station can transmit the carrier identifier of the first target uplink carrier to the terminal device so that the terminal device can determine, among the SUL carrier and the non-SUL carrier, the first target uplink carrier configured by the base station and transmit the random access preamble on the first target uplink carrier. 
     In the technical solutions provided in the embodiments of the disclosure, the base station can configure, among the plurality of uplink carrier, configure the first target uplink carrier for the terminal device to transmit the random access preamble to enable the terminal device to transmit the random access preamble to the base station using the first target uplink carrier to initiate the random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 2B , the operation  202  of transmitting a carrier identifier of a first target uplink carrier to a terminal device can be implemented by operation  2021 . 
     In operation  2021 , an RRC message including the carrier identifier of the first target uplink carrier is transmitted to the terminal device. 
     Exemplarily, the RRC message is information transmitted by a base station to the terminal device to regulate and control resource configuration. As a result, after the terminal device accesses the base station, the base station can write the carrier identifier of the first target uplink carrier into the RRC message and transmit the RRC message to the terminal device while the base station configures other uplink resource or downlink resource for the terminal device via the RRC message. 
     Specifically, a first function field can be added in the RRC message in advance and pre-agreed between two sides: the terminal device and the base station. After obtaining the first target uplink carrier, the base station can write the carrier identifier of the first target uplink carrier into the first function field. After receiving the RRC message, the terminal device can obtain a first carrier identifier by parsing the first function field and determine, as the first target uplink carrier, a carrier corresponding to the first carrier identifier in the SUL and non-SUL carrier included by the base station. 
     In the technical solutions provided in the embodiments of the disclosure, the base station can configure, among a plurality of uplink carriers, the first target uplink carrier for the terminal device to transmit a random access preamble and notify the terminal device via the RRC message to enable the terminal device to transmit the random access preamble to the base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 2C , the operation  202  of transmitting a carrier identifier of a first target uplink carrier to a terminal device can be implemented by operation  2022 . 
     In operation  2022 , allocation information of a random access preamble is transmitted to the terminal device, the allocation information of the random access preamble including the carrier identifier of the first target uplink carrier. 
     Exemplarily, when triggering an non-competitive random access using a PDCCH command, the base station can allocate a random access preamble to the terminal device according to a preset rule and concurrently obtain, among a plurality of uplink carriers, a carrier where the PDCCH is on, as the first target uplink carrier configured for the terminal device to transmit the random access preamble; the base station can then generate the allocation information of the random access preamble according to the random access preamble and the carrier identifier of the first target uplink carrier, and transmit the allocation information of the random access preamble to the terminal device. 
     In the technical solutions provided in the embodiments of the disclosure, in the non-competitive random access, the base station can configure, among the plurality of uplink carriers, the first target uplink carrier for the terminal device to transmit the random access preamble and notify the terminal device via the allocation information of the random access preamble to enable to terminal device to transmit the random access preamble to the base station using the first target uplink carrier to initiate the random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 2D , the operation  201  of obtaining, among a plurality of uplink carriers, a first target uplink carrier configured for a terminal device to transmit a random access preamble can be implemented by operations  2011  and  2012 ; the operation  202  of transmitting a carrier identifier of the first target uplink carrier to the terminal device can be implemented by operation  2023 . 
     In operation  2011 , a handover request is received from an original base station, the handover request indicating that the terminal device performs handover from the original base station to the base station. 
     In operation  2012 , the first target uplink carrier configured for the terminal device to transmit the random access preamble among the plurality of uplink carriers is obtained according to the handover request. 
     In operation  2023 , handover response information is transmitted to the original base station, the handover response information including the carrier identifier of the first target uplink carrier to enable the original base station to transmit, to the terminal device, handover command information including the carrier identifier of the first target uplink carrier. 
     Exemplarily, during usage, the terminal device may perform handover between the base stations. When detecting that the terminal devices needs to perform the handover between the base stations, an original base station accessed currently by the terminal device can transmit a handover request to a base station that the terminal device is about to access. After receiving the handover, the base station can obtain, among an SUL carrier and a non-carrier carrier, a carrier where a PDCCH is on, as the first target uplink carrier configured for the terminal device to transmit a random access preamble; and then generate handover request response information according to a carrier identifier of the first target uplink carrier, and transmit the handover request response information to the original base station. In a practical application, the handover request response information also includes the carrier identifier of the SUL carrier and the carrier identifier of the non-SUL carrier. The original base station can generate handover command information according to the handover request response information and the handover command information includes the carrier identifier of the SUL carrier, the carrier identifier of the non-SUL carrier and the carrier identifier of the first target uplink carrier and transmit the handover command information to the terminal device. 
     In a practical application, a function field can be added in the handover request response information and the handover command information. Then the function field can be configured to carry the carrier identifier of the first target uplink carrier. 
     In the technical solutions provided in the embodiments of the disclosure, when the terminal device performs the handover between the base stations, the base station can configure, among the plurality of uplink carriers, the first target uplink carrier for the terminal device to transmit the random access preamble and notify the original base station via the handover response information, so that the original base station can notify the terminal device and the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 2E , the operation  202  of transmitting a carrier identifier of a first target uplink carrier to a terminal device can be implemented by operation  2024 . 
     In operation  2024 , after re-establishing or modifying an SCG, a base station transmits a reconfiguration message to the terminal device and the reconfiguration message including the carrier identifier of the first target uplink carrier. 
     Exemplarily, the base station may re-establish or modify the SCG in the cells and may reconfigure a carrier used for transmitting a random access preamble for a terminal device after re-establishing or modifying the SCG because different SCGs maintain different resources. According to an embodiment of the disclosure, after re-establishing or modifying the SCG, the base station obtains, among the SUL carrier and non-SUL carrier, a carrier where a current PDCCH is on and configures the obtained carrier as the first target uplink carrier for the terminal device to transmit a random access preamble. Because after re-establishing or modifying the SCG, the base station needs to transmit the reconfiguration message to the terminal device to notify the terminal device of a latest resource configuration situation. As a result, the base station can carry the carrier identifier of the first target uplink carrier in the reconfiguration message and transmit the reconfiguration message to the terminal device. 
     In the technical solutions provided in the embodiments of the disclosure, when re-establishing or modifying the SCG, the base station notifies the terminal device, via the reconfiguration message, of the first target uplink carrier configured for the terminal device to transmit the random access preamble, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     In an embodiment of the disclosure, as illustrated in the  FIG. 2F , the method further includes operations  203  and  204 . 
     In operation  203 , a second target uplink carrier configured for a terminal device to transmit scheduled transmission information is obtained among a plurality of uplink carriers according to a random access preamble transmitted by the terminal device. 
     In operation  204 , random access response information is transmitted to the terminal device, the random access response information including the carrier identifier of the second target uplink carrier. 
     Exemplarily, during a competitive random access, the base station receives the random access preamble from the terminal from the terminal device and can obtain, among an SUL carrier and a non-SUL carrier, a carrier where a PDCCH is on, as the second target uplink carrier used by the terminal device to transmit scheduled transmission information, and then carry the carrier identifier of the second target uplink carrier in the random access response information, and notify the terminal device of the random access response information. After obtaining the random access response information, the terminal device obtains, among the SUL carrier and the non-SUL carrier, a carrier with a carrier identifier same as the carrier identifier included by the random access response information, as a carrier for transmitting the scheduled transmission information, herein the carrier is the second target uplink carrier configured for the terminal device by the base station. In a practical application, the second target uplink carrier can be same as or different from the first target uplink carrier. There are no limits made in the embodiments of the disclosure. 
     In the technical solutions provided in the embodiments of the disclosure, the base station can also configure the second target uplink carrier for the terminal device to transmit the scheduled transmission message and notify the terminal device via the random access response information, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     The technical solutions in the embodiments of the disclosure will be described below by means of a specific embodiment of the disclosure. 
     First Embodiment 
       FIG. 3  is an interaction diagram illustrating a random access method according to an exemplary embodiment. The random access method is applied to a terminal device and a base station, herein the base station includes: two uplink carriers including one SUL carrier and one non-SUL carrier, and one downlink carrier. As illustrated in  FIG. 3 , the method includes the following operations  301  to  311 . 
     In operation  301 , the base station broadcasts a system message. 
     The system information includes a carrier identifier of the SUL carrier, a carrier identifier of the non-SUL carrier and a carrier identifier of the downlink carrier. Usually, the carrier identifier of the SUL carrier can be a frequency of the SUL carrier and the carrier identifier of the non-SUL carrier can be a frequency of the non-SUL carrier and the carrier identifier of the downlink carrier can be a frequency of the downlink carrier. 
     In operation  302 , the terminal device accesses the base station according to the system message. 
     In operation  303 , when the terminal device is in a connected state and an uplink out-of-synchronization situation exists, the base station allocate a random access preamble to the terminal device, obtain, among the two uplink carriers, a carrier where a PUCCH is on, as the first target uplink carrier. 
     In operation  304 , the base station generates allocation information of the random access preamble according to the random access preamble and the carrier identifier of the first target uplink carrier. 
     In operation  305 , the base station transmits the allocation information of the random access preamble to the terminal device. 
     In operation  306 , the terminal device obtains the carrier identifier included by the allocation information of the random access preamble. 
     Exemplarily, the carrier identifier can be a carrier frequency. 
     In operation  307 , the terminal device obtains, as the first target uplink carrier, a carrier corresponding to the carrier identifier among the SUL carrier and the non-SUL carrier. 
     In operation  308 , the terminal device transmits the random access preamble to the base station using the first target uplink carrier. 
     If the random access response information is not received from the base station in a second preset period, the terminal device transmits the random access preamble using another uplink carrier other than the first target uplink carrier. Exemplarily, a transmitting power with which the terminal transmits the random access preamble for the second time can be same as the transmitting power with which the terminal transmits the random access preamble for the first time. 
     In operation  309 , the base station generates the random access response information according to the random access preamble. 
     In operation  310 , the base station transmits the random access response information to the terminal device. 
     In operation  311 , the terminal device initiates a random access according to the random access response information. 
     In a random access method provided in the embodiments of the disclosure, the base station can configure the first target uplink carrier for the terminal device to transmit the random access preamble and notify the terminal device via the allocation information of the random access preamble when the base station is in the uplink out-of-synchronization situation. The terminal device can transmit, on the first target uplink carrier, the random access preamble to a target base station according to configuration of the base station, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     Second Embodiment 
       FIG. 4  is an interaction diagram illustrating a random access method according to an exemplary embodiment. The random access method is applied to a terminal device, an original base station and a target base station, herein the target base station includes: two uplink carriers including one SUL carrier and one non-SUL carrier, and one downlink carrier. As illustrated in  FIG. 4 , the method includes the following operations  401  to  417 . 
     In operation  401 , if it is detected that the terminal device needs to perform handover to the target base station, the original base station transmits a handover request to the target base station. 
     In operation  402 , the target base station obtains a random access resource of an SUL carrier and a random access resource of a non-SUL carrier respectively according to the handover request. 
     In operation  403 , the target base station determines a first target uplink carrier configured for the terminal device according to the random access resource of the SUL carrier and the random access resource of the non-SUL carrier. 
     In operation  404 , the target base station generates handover response information according to a carrier identifier of the first target uplink carrier and a carrier identifier of the SUL carrier and a carrier identifier of the non-SUL carrier. 
     In operation  405 , the target base station transmits the handover response information to the original base station. 
     In operation  406 , the original base station generates handover command information according to the carrier identifier of the first target uplink carrier and the carrier identifier of the SUL carrier and the carrier identifier of the non-SUL carrier included by the handover response information. 
     In operation  407 , the original base station transmits the handover command information to the terminal. 
     In operation  408 , after performing the handover to the target base station, if the terminal device determines to initiate a random access, the terminal device determines, among the SUL carrier and the non-SUL carrier included by the target base station, an uplink carrier with the carrier identifier same as the carrier identifier of the first target uplink carrier included in the handover command information as the first target uplink carrier. 
     In operation  409 , the terminal device transmits a random access preamble to the target base station using the first target uplink carrier. 
     If random access response information is not received from the base station in a second preset period, the terminal device transmits the random access preamble using another uplink carrier other than the first target uplink carrier. 
     In operation  410 , according to the random access preamble, the target base station determines, among the SUL carrier and the non-SUL carrier, a carrier where a PUCCH is as a second target uplink carrier. 
     In operation  411 , the target base station generates random access response information according to the carrier identifier of the second target uplink carrier. 
     In operation  412 , the target base station transmits the random access response information to the terminal device. 
     In operation  413 , the terminal device determines, among the SUL carrier and the non-SUL carrier, an uplink carrier corresponding to the carrier identifier included by the random access response information as the second target uplink carrier. 
     In operation  414 , the terminal device transmits scheduled transmission information to the target base station using the second target uplink carrier. 
     In operation  415 , the target base station generates conflict-solving information according to the scheduled transmission information. 
     In operation  416 , the target base station transmits the conflict-solving information to the terminal device. 
     In operation  417 , the terminal device implements the random access according to the conflict-solving information. 
     In a random access method provided in the embodiments of the disclosure, the target base station can configure the first target uplink carrier for the terminal device to transmit the random access preamble and notifies the terminal device via allocation information of the random access preamble when the terminal device performs the handover between the base stations. The terminal device can transmit, on the first target uplink carrier, the random access preamble to the target base station according to configuration of the base station, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     Third Embodiment 
       FIG. 5  is an interaction diagram illustrating a random access method according to an exemplary embodiment. The random access method is applied to a terminal device and a base station, herein the base station includes: two uplink carriers including one SUL carrier and one non-SUL carrier, and one downlink carrier. As illustrated in  FIG. 5 , the method includes the following operations  501  to  516 . 
     In operation  501 , the base station broadcasts a system message. 
     The system information includes a carrier identifier of the SUL carrier, a carrier identifier of the non-SUL carrier and a carrier identifier of the downlink carrier. Usually, the carrier identifier of the SUL carrier can be a frequency of the SUL carrier and the carrier identifier of the non-SUL carrier can be a frequency of the non-SUL carrier and the carrier identifier of the downlink carrier can be a frequency of the downlink carrier. 
     In operation  502 , the terminal device accesses the base station according to the system message. 
     In operation  503 , if the base station re-establishes or modifies an SCG for a current cell, the base station obtain a random access resource included by the SUL carrier and a random access resource included by the non-SUL carrier after the re-establishment or the modification. 
     In operation  504 , the base station obtains a first target uplink carrier configured for the terminal device according to the random access resource included by the SUL carrier and the random access resource included by the non-SUL carrier. 
     In operation  505 , the base station generates a reconfiguration message according to the carrier identifier of the first target uplink carrier. 
     In operation  506 , the base station transmits the reconfiguration message to the terminal device. 
     In operation  507 , the terminal device obtains, among the SUL carrier and the non-SUL carrier, a carrier corresponding to the carrier identifier included in the reconfiguration message, as the first target uplink carrier. 
     In operation  508 , when a random access is needed, the terminal device transmit a random access preamble to the base station using the first target uplink carrier. 
     If random access response information is not received from the base station in a second preset period, the terminal device transmits the random access preamble using another uplink carrier other than the first target uplink carrier. 
     In operation  509 , according to the random access preamble, the base station determines, among the SUL carrier and the non-SUL carrier, a carrier where a PUCCH is as a second target uplink carrier. 
     In operation  510 , the base station generates random access response information according to the carrier identifier of the second target uplink carrier. 
     In operation  511 , the base station transmits the random access response information to the terminal device. 
     In operation  512 , the terminal device determines, as the second target uplink carrier, an uplink carrier corresponding to the carrier identifier included by the random access response information. 
     In operation  513 , the terminal device transmits scheduled transmission information to the base station using the second target uplink carrier. 
     In operation  514 , the base station generates conflict-solving information according to the scheduled transmission information. 
     In operation  515 , the base station transmits the conflict-solving information to the terminal device. 
     In operation  516 , the terminal device implements a random access according to the conflict-solving information. 
     In a random access method provided in the embodiments of the disclosure, a target base station can configure the first target uplink carrier for the terminal device to transmit the random access preamble and notify the terminal device via allocation information of the random access preamble when the terminal device performs handover between the base stations. The terminal device can transmit, on the first target uplink carrier, the random access preamble to the target base station according to configuration of the base station, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     The device embodiments of the disclosure below can be used to implement the method embodiments of the disclosure. 
       FIG. 6A  is a block diagram illustrating a random access device  60  according to an exemplary embodiment and the device  60  can be implemented and become a part or all of an electrical device via software, hardware or a combination of the software and the hardware. As illustrated in  FIG. 6A , the random access device  60  includes a first determination module  601  and a first transmitting module  602 . 
     The first determination module  601  is configured to determine a first target uplink carrier among a plurality of uplink carriers corresponding to a target base station, the plurality of uplink carriers including at least one SUL carrier. 
     The first transmitting module  602  is configured to transmit a random access preamble to the target base station using the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6B , the first determination module  601  includes a first receiving sub-module  6011  and a first determination sub-module  6012 . 
     The first receiving sub-module  6011  is configured to receive a carrier identifier of the first target uplink carrier from a base station. 
     The first determination sub-module  6012  is configured to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6C , the first receiving sub-module  6011  includes a first receiving unit  6011   a . The first receiving unit  6011   a  is configured to receive an RRC message from the target base station, the RRC message including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6D , the first receiving sub-module  6011  includes a second receiving unit  6011   b . The second receiving unit  6011   b  is configured to receive allocation information of the random access preamble from the target base station, the random access preamble including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6E , the first receiving sub-module  6011  includes a third receiving unit  6011   c . The third receiving unit  6011   c  is configured to receive handover command information from an original base station when the terminal device performs handover between the original base station and the target base station, the handover command information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6F , the first receiving sub-module  6011  includes a fourth receiving unit  6011   d . The fourth receiving unit  6011   d  is configured to receive a reconfiguration message from the target base station after the target base station re-establishes an SCG or modifies the SCG, the reconfiguration message including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6G , the first determination module  601  includes a second receiving sub-module  6013 , a first detection sub-module  6014  and a second determination sub-module  6015 . 
     The second receiving sub-module  6013  is configured to receive an RRC message including a power threshold from the target base station. 
     The first detection sub-module  6014  is configured to detect an RSRP of a current downlink carrier. 
     The second determination sub-module  6015  is configured to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station, according to the RSRP and the power threshold. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6H , the plurality of uplink carriers includes one SUL carrier and one non-SUL carrier; the second determination sub-module  6015  includes a first determination unit  6015   a  and a second determination unit  6015   b.    
     The first determination unit  6015   a  is configured to determine the non-SUL carrier as the first target uplink carrier in response to the RSRP being greater than or equal to the power threshold. 
     The second determination unit  6015   b  is configured to determine the SUL carrier as the first target uplink carrier in response to the RSRP being less than the power threshold. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6I , the first determination module  601  includes a third receiving sub-module  6016 , a second detection sub-module  6017  and a third determination sub-module  6018 . 
     The third receiving sub-module  6016  is configured to receive an RRC message including a quality threshold from the target base station. 
     The second detection sub-module  6017  is configured to detect an RSRQ of the current downlink carrier. 
     The third determination sub-module  6018  is configured to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRQ and the quality threshold. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6J , the plurality of uplink carriers includes on SUL carrier and one non-SUL carrier; the third determination sub-module  6018  includes a third determination unit  6018   a  and a fourth determination unit  6018   b.    
     The third determination unit  6018   a  is configured to determine the non-SUL carrier as the first target uplink carrier in response to the RSRQ being greater than or equal to the quality threshold. 
     The fourth determination unit  6018 b is configured to determine the SUL carrier as the first target uplink carrier in response to the RSRQ being less than the quality threshold. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6K , the first determination module  601  includes a fourth receiving sub-module  6019 , a third detection sub-module  6110  and a fourth determination sub-module  6011 . 
     The fourth receiving sub-module  6019  is configured to receive, from the target base station, an RRC message including a power threshold and a quality threshold. 
     The third detection sub-module  6110  is configured to detect the RSRP and the RSRQ of the current downlink carrier. 
     The fourth determination sub-module  6011  is configured to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold as well as the RSRQ and the quality threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers includes one SUL and one non-SUL. As illustrated in  FIG. 6L , the fourth determination sub-module  6111  includes a fifth determination unit  6111   a  and a sixth determination unit  6111   b.    
     The fifth determination unit  6111   a  is configured to determine the non-SUL carrier as the first target uplink carrier when the RSRP is greater than or equal to the power threshold, or the RSRQ is greater than or equal to the quality threshold. 
     The sixth determination unit  6111   b  is configured to determine the SUL carrier as the first target uplink carrier in response to the RSRP being less than the power threshold and the RSRQ being less than the quality threshold. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6M , the first determination module  601  includes a fifth determination sub-module  6112  configured to determine, as the first target uplink carrier, a carrier configured with a PUCCH among the plurality of uplink carriers. 
     In an embodiment of the disclosure, as illustrated in  FIG. 6N , the first determination module  601  includes a sixth determination sub-module  6113 . The sixth determination sub-module  6113  is configured to determine the first target uplink carrier according to a random access resource included by each of the plurality of uplink carriers. 
     In an embodiment of the disclosure, as illustrated in  FIG. 60 , the device  60  further includes a receiving module  603 , a second determination module  604  and a second transmitting module  605 . 
     The receiving module  603  is configured to receive random access response information from the target base station, the random access response information including a fifth carrier identifier. 
     The second determination module  604  is configured to determine a second target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the fifth carrier identifier. 
     The second transmitting module  605  is configured to transmit scheduled transmission information to the target base station using the second target uplink carrier. 
     The above embodiment of the disclosure is also suitable for the random access device  60  illustrated in  FIG. 6A  to  FIG. 6N . 
     In an embodiment of the disclosure, as illustrated in  FIG. 6P , the device  60  further includes a third determination module  606  and a third transmitting module  607 . 
     The third determination module  606  is configured to determine a third target uplink carrier among the plurality of uplink carriers corresponding to the target base station if the random access response information is not received from the target base station in a second preset period. 
     The third transmitting module  607  is configured to transmit the random access preamble to the target base station using the third target uplink carrier. 
     The above embodiment of the disclosure is also suitable for the random access device  60  illustrated in  FIG. 6A  to  FIG. 6N . 
     In an embodiment of the disclosure, as illustrated in  FIG. 6Q , the third transmitting module  607  includes a first obtaining sub-module  6071  and a first transmitting sub-module  6072 . 
     The first obtaining sub-module  6071  is configured to obtain a transmitting power with which the random access preamble is transmitted to the target base station using the first target uplink carrier. 
     The first transmitting sub-module  6072  is configured to transmit the random access preamble to the target base station on the third target uplink carrier with the transmitting power. 
     A random access device is provided in the embodiments of the disclosure and the device can determine, among the plurality of uplink carriers corresponding to the target base station, the first target uplink carrier used for transmitting the random access preamble and transmit the random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
       FIG. 7A  is a block diagram illustrating a random access device  70  according to an exemplary embodiment and the device  70  can be implemented and become a part or all of an electrical device via software, hardware or a combination of the software and the hardware. According to  FIG. 7A , the random access device  70  includes a fourth transmitting module  701 . 
     The fourth transmitting module  701  is configured to transmit indication information to a terminal device, the indication information being configured to indicate a first target uplink carrier to be determined, by the terminal device for transmitting a random access preamble, among a plurality of uplink carriers corresponding to the base station, and the plurality of uplink carriers including at least one SUL carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7B , the device  70  also includes a first obtaining module  702  and the fourth transmitting module includes a first transmitting sub-module  7011 . 
     The first obtaining module  702  is configured to obtain the first target uplink carrier, configured for the terminal device to transmit the random access preamble, among the plurality of uplink carriers. 
     The first transmitting sub-module  7011  is configured to transmit a carrier identifier of the first target uplink carrier to the terminal device to enable the terminal device to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the base station according to the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7C , the second obtaining sub-module  7021  is configured to obtain the first target uplink carrier configured for the terminal device to transmit the random access preamble according to a random access resource included by each of the plurality of uplink carriers. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7D , the first transmitting sub-module  7011  includes a first transmitting unit  7011   a  configured to transmit an RRC message to the terminal device, the RRC message including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7E , the first transmitting sub-module  7011  includes a second transmitting unit  7011   b  configured to transmit allocation information of the random access preamble to the terminal device, the allocation information of the random access preamble including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7F , the first obtaining module  702  includes a seventh receiving sub-module  7022  and a third obtaining sub-module  7023 ; and the first transmitting sub-module  7011  includes a third transmitting unit  7011   c.    
     The seventh receiving sub-module  7022  is configured to receive a handover request from an original base station, the handover request indicating that the terminal device performs a handover from the original base station to the base station. 
     The third obtaining sub-module  7023  is configured to obtain the first target uplink carrier, configured for the terminal device to transmit the random access preamble, among the plurality of uplink carriers according to the handover request. 
     The third transmitting unit  7011   c  is configured to transmit handover response information to the original base station, the handover response information including the carrier identifier of the first target uplink carrier to enable the original base station to transmit handover command information including the carrier identifier of the first target uplink carrier to the terminal device. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7G , the first transmitting sub-module  7011  includes a fourth transmitting unit  7111   d . The fourth transmitting unit  7111   d  is configured to transmit reconfiguration information to the terminal device after the base station re-establishes an SCG or modifies the SCG, the reconfiguration information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7H , the fourth transmitting module includes a second transmitting sub-module  7012 . The second transmitting sub-module  7012  is configured to transmit a power threshold to the terminal device to enable the terminal device to determine the first target uplink carrier for transmitting the random access preamble, among the plurality of uplink carriers corresponding to the base station, according to the power threshold and an RSRP of a current downlink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7I , the fourth transmitting module  701  includes a third transmitting sub-module  7013  configured to transmit a quality threshold to the terminal device to enable the terminal device to determine the first target uplink carrier for transmitting the random access preamble, among the plurality of uplink carriers corresponding to the base station, according to the quality threshold and an RSRQ of a current downlink carrier. 
     In an embodiment of the disclosure, as illustrated in  FIG. 7J , the device  70  further includes a second obtaining module  703  and a fifth transmitting module  704 . 
     The second obtaining module  703  is configured to obtain the second target uplink carrier, configured for the terminal device to transmit scheduled transmission information, among the plurality of uplink carriers according to the random access preamble transmitted by the terminal device. 
     The fifth transmitting module  704  is configured to transmit random access response information to the terminal device, the random access response information including the carrier identifier of the second target uplink carrier. 
     The above embodiment of the disclosure is also suitable for the random access device  70  illustrated in  FIG. 7A  to  FIG. 7I . 
     A random access device is provided in the embodiments of the disclosure and the device can determine, among the plurality of uplink carriers, the first target uplink carrier for transmitting the random access preamble and transmit the random access preamble to the target base station using the first target uplink carrier, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     The embodiments of the disclosure further provide a random access device which includes: 
     a first processor; 
     a first memory configured to store instructions executable by the first processor; 
     The first processor is configured to: 
     determine a first target uplink carrier among a plurality of uplink carriers corresponding to a target base station, the plurality of uplink carriers including at least one SUL carrier; and 
     transmit a random access preamble to the target base station using the first target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to receive a carrier identifier of the first target uplink carrier from the base station and determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to receive an RRC message including the carrier identifier of the first target uplink carrier from the target base station. 
     In an embodiment of the disclosure, the above first processor is also configured to receive allocation information of the random access preamble from the target base station, the random access preamble including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to receive handover command information from an original base station when the terminal device performs handover between the original base station and the target base station, the handover command information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to receive a reconfiguration message from the target base station after the target base station re-establishes an SCG or modifies the SCG, the reconfiguration message including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to receive an RRC message including a power threshold from the target base station, detect an RSRP of a current downlink carrier and determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station, according to the RSRP and the power threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers include one SUL carrier and one non-SUL carrier; the above first processor is also configured to determine the non-SUL carrier as the first target uplink carrier in response to the RSRP being greater than or equal to the power threshold, and determine the SUL carrier as the first target uplink carrier in response to the RSRP being less than the power threshold. 
     In an embodiment of the disclosure, the above first processor is also configured to receive an RRC message including a quality threshold from the target base station, detect the RSRQ of the current downlink carrier and determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station, according to the RSRQ and the quality threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers include one SUL carrier and one non-SUL carrier; the above first processor is also configured to determine the non-SUL carrier as the first target uplink carrier in response to the RSRQ being greater than or equal to the quality threshold, and determine the SUL carrier as the first target uplink carrier in response to the RSRQ being less than the quality threshold. 
     In an embodiment of the disclosure, the above first processor is also configured to receive, from the target base station, an RRC message including the power threshold and the quality threshold, detect the RSRP and the RSRQ of the current downlink carrier and determine the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold as well as the RSRQ and the quality threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers include one SUL carrier and one non-SUL carrier; the above first processor is also configured to determine the non-SUL carrier as the first target uplink carrier when the RSRP is greater than or equal to the power threshold, or the RSRQ is greater than or equal to the quality threshold; and determine the SUL carrier as the first target uplink carrier when the RSRP is less than the power threshold and the RSRQ is less than the quality threshold. 
     In an embodiment of the disclosure, the above first processor is also configured to determine, as the first target uplink carrier, a carrier configured with a PUCCH among the plurality of uplink carriers. 
     In an embodiment of the disclosure, the above first processor is also configured to determine the first target uplink carrier according to a random access resource included by each of the plurality of uplink carriers. 
     In an embodiment of the disclosure, the above first processor is also configured to receive, from the target base station, random access response information including the carrier identifier of a second target uplink carrier, determine, according to the carrier identifier of the second target uplink carrier, the second target uplink carrier among the plurality of uplink carriers corresponding to the target base station and transmit scheduled transmission information to the target base station using the second target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to determine a third target uplink carrier among the plurality of uplink carriers corresponding to the target base station if the random access response information is not received from the target base station in a second preset period and transmit the random access preamble to the target base station using the third target uplink carrier. 
     In an embodiment of the disclosure, the above first processor is also configured to obtain a transmitting power with which the random access preamble is transmitted to the target base station using the first target uplink carrier and transmit the random access preamble to the target base station on the third target uplink carrier with the transmitting power. 
     A random access device is provided in the embodiments of the disclosure and the device can determine, among the plurality of uplink carriers corresponding to the target base station, the first target uplink carrier used for transmitting the random access preamble and transmit the random access preamble to the target base station using the first target uplink carrier to initiate a random access, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     The embodiments of the disclosure further provide a random access device which includes: 
     a second processor; 
     a second memory configured to store instructions executable by the second processor; 
     The second processor is configured to: 
     transmit indication information to a terminal device, the indication information being configured to indicate a first target uplink carrier to be determined, by the terminal device for transmitting a random access preamble, among a plurality of uplink carriers corresponding to a base station, and the plurality of uplink carriers including at least one SUL carrier. 
     In an embodiment of the disclosure, the above second processor is also configured to obtain the first target uplink carrier, configured for the terminal device to transmit the random access preamble, among the plurality of uplink carriers and transmit a carrier identifier of the first target uplink carrier to the terminal device to enable the terminal device to determine the first target uplink carrier among the plurality of uplink carriers corresponding to the base station according to the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above second processor is also configured to obtain the first target uplink carrier configured for the terminal device to transmit the random access preamble according to a random access resource included by each of the plurality of uplink carriers. 
     In an embodiment of the disclosure, the above second processor is also configured to transmit an RRC message including the carrier identifier of the first target uplink carrier to the terminal device. 
     In an embodiment of the disclosure, the above second processor is also configured to transmit allocation information of the random access preamble to the terminal device, the allocation information of the random access preamble including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above second processor is also configured to receive a handover request, which indicates that the terminal device performs a handover from the original base station to the base station, from an original base station, obtain the first target uplink carrier, configured for the terminal device to transmit the random access preamble, among the plurality of uplink carriers according to the handover request and transmit handover response information to the original base station, the handover response information including the carrier identifier of the first target uplink carrier to enable the original base station to transmit handover command information including the carrier identifier of the first target uplink carrier to the terminal device. 
     In an embodiment of the disclosure, the above second processor is also configured to transmit reconfiguration information to the terminal device after the base station re-establishes an SCG or modifies the SCG and the reconfiguration information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, the above second processor is also configured to transmit a power threshold to the terminal device to enable the terminal device to determine the first target uplink carrier for transmitting the random access preamble, among the plurality of uplink carriers corresponding to the base station, according to the power threshold and an RSRP of a current downlink carrier. 
     In an embodiment of the disclosure, the above second processor is also configured to transmit a quality threshold to the terminal device to enable the terminal device to determine the first target uplink carrier for transmitting the random access preamble, among the plurality of uplink carriers corresponding to the base station, according to the quality threshold and an RSRQ of a current downlink carrier. 
     In an embodiment of the disclosure, the above second processor is also configured to obtain the second target uplink carrier, configured for the terminal device to transmit scheduled transmission information, among the plurality of uplink carriers according to the random access preamble transmitted by the terminal device. 
     A random access device is provided in the embodiments of the disclosure and the device can determine, among the plurality of uplink carriers, the first target uplink carrier for transmitting the random access preamble and transmit the random access preamble to the target base station using the first target uplink carrier, so that the random access is implemented in cells configured with the SUL carrier, thus the success rate of the random access is increased. 
     As to the device according to the above embodiments, detailed operations performed by respective modules in the device are already described in detailed in the embodiments related to the method, and will not be elaborated herein. 
       FIG. 8  is a structural block diagram illustrating a random access device  80  according to an exemplary embodiment. For example, the device  80  may be a mobile phone, a computer, a digital broadcast terminal, a messaging device, a gaming console, a tablet, a medical device, exercise equipment and a personal digital assistant and so on. 
     The device  80  may include one or more of the following components: a processing component  802 , a memory  804 , a power component  806 , a multimedia component  808 , an audio component  810 , an Input/Output (I/O) interface  812 , a sensor component  814 , and a communication component  816 . 
     The processing component  802  typically controls overall operations of the device  80 , such as the operations associated with display, telephone calls, data communications, camera operations, and recording operations. The processing component  802  may include one or more processors  820  to execute instructions to perform all or part of the operations in the above-mentioned method. Moreover, the processing component  802  may include one or more modules which facilitate interaction between the processing component  802  and the other components. For instance, the processing component  802  may include a multimedia module to facilitate interaction between the multimedia component  808  and the processing component  802 . 
     The memory  804  is configured to store various types of data to support the operation of the device  80 . Examples of such data include instructions for any application programs or methods operated on the device  80 , contact data, phonebook data, messages, pictures, video, etc. The memory  804  may be implemented by any type of volatile or non-volatile memory devices, or a combination thereof, such as a Static Random Access Memory (SRAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), an Erasable Programmable Read-Only Memory (EPROM), a Programmable Read-Only Memory (PROM), a Read-Only Memory (ROM), a magnetic memory, a flash memory, and a magnetic or optical disk. 
     The power component  806  provides power for various components of the device  80 . The power component  806  may include a power management system, one or more power supplies, and other components associated with generation, management and distribution of power for the device  80 . 
     The multimedia component  808  includes a screen providing an output interface between the device  1100  and a user. In some embodiments, the screen may include a Liquid Crystal Display (LCD) and a Touch Panel (TP). If the screen includes the TP, the screen may be implemented as a touch screen to receive an input signal from the user. The TP includes one or more touch sensors to sense touches, swipes and gestures on the TP. The touch sensors may not only sense a boundary of a touch or swipe action but also detect a duration and pressure associated with the touch or swipe action. In some embodiments, the multimedia component  808  includes a front camera and/or a rear camera. The front camera and/or the rear camera may receive external multimedia data when the device  80  is in an operation mode, such as a photographing mode or a video mode. The front camera and/or the rear camera may receive external multimedia data when the device  80  is in an operation mode, such as a photographing mode or a video mode. 
     The audio component  810  is configured to output and/or input an audio signal. For example, the audio component  810  includes a Microphone (MIC), and the MIC is configured to receive an external audio signal when the device  80  is in an operation mode, such as a call mode, a recording mode and a voice recognition mode. The received audio signal may further be stored in the memory  804  or sent through the communication component  816 . In some embodiments, the audio component  810  further includes a speaker configured to output the audio signal. 
     The I/O interface  812  provides an interface between the processing component  802  and a peripheral interface module, and the peripheral interface module may be a keyboard, a click wheel, a button and the like. The button may include, but not limited to: a home button, a volume button, a starting button and a locking button. 
     The sensor component  814  includes one or more sensors configured to provide status assessment in various aspects for the device  80 . For instance, the sensor component  814  may detect an on/off status of the device  80  and relative positioning of components, such as a display and small keyboard of the device  80 , and the sensor component  814  may further detect a change in a position of the device  80  or a component of the device  80 , presence or absence of contact between the user and the device  80 , orientation or acceleration/deceleration of the device  1100  and a change in temperature of the device  80 . he sensor component  814  may include a proximity sensor configured to detect presence of an object nearby without any physical contact. The sensor component  814  may also include a light sensor, such as a Complementary Metal Oxide Semiconductor (CMOS) or Charge Coupled Device (CCD) image sensor, configured for use in an imaging application. In some embodiments, the sensor component  814  may also include an acceleration sensor, a gyroscope sensor, a magnetic sensor, a pressure sensor or a temperature sensor. 
     The communication component  816  may be a transceiver, and is configured to facilitate wired or wireless communication between the device  80  and another device. The device  80  may access a communication-standard-based wireless network, such as a Wireless Fidelity (WiFi) network, a 2nd-Generation (2G) or 3rd-Generation ( 3 G) network or a combination thereof. In an exemplary embodiment, the communication component  816  receives a broadcast signal or broadcast associated information from an external broadcast management system through a broadcast channel. In an exemplary embodiment, the communication component  816  further includes a Near Field Communication (NFC) module to facilitate short-range communication. For example, the NFC module may be implemented based on a Radio Frequency Identification (RFID) technology, an Infrared Data Association (IrDA) technology, an Ultra-WideBand (UWB) technology, a Bluetooth (BT) technology and another technology. 
     In an exemplary embodiment, the device  1100  may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), controllers, micro-controllers, microprocessors or other electronic components, and is configured to execute the abovementioned method. 
     In an exemplary embodiment, there is also provided a non-transitory computer-readable storage medium including an instruction, such as the memory  804  including an instruction, and the instruction may be executed by the processor  820  of the device  80  to implement the abovementioned method. For example, the non-transitory computer-readable storage medium may be a Read-Only Memory (ROM), a Random Access Memory (RAM), a Compact Disc Read-Only Memory (CD-ROM), a magnetic tape, a floppy disc, an optical data storage device and the like. 
       FIG. 9  is a structural block diagram illustrating a random access device  90  according to an exemplary embodiment. For example, the device  90  may be provided as a server that is applied to a base station. The device  90  includes a processing component  902  and further includes one or more processors and a memory resource represented by a memory  902 , which stores instructions (such as an application) executable by the processing component  902 . The applications stored in the memory  903  may include one or more modules, each of which corresponds to a group of instructions. Moreover, the processing component  902  is configured to execute the instructions to perform the above methods. 
     The device  90  may further include a power component  906 , which is configured to conduct power management of the device  90 , one wired or wireless network interface  905 , which is configured to connect the device  90  to a network and one I/O interface  908 . The device  90  can operate an operation system stored in the memory  903 , such as Windows Server™, Mac OS X™, Unix™, Linux™, FreeBSD™ and the like. 
     A non-transitory computer readable storage medium is provided in the embodiments of the disclosure. When instructions in the storage medium is executed by the processor of the device  80 , the device  80  can execute the above random access method at the terminal device side. The method includes the following operations. 
     A first target uplink carrier is determined among a plurality of uplink carriers corresponding to a target base station, the plurality of uplink carriers including at least one SUL carrier. 
     A random access preamble is transmitted to the target base station using the first target uplink carrier. 
     In an embodiment of the disclosure, determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station includes the following operations: a carrier identifier of the first target uplink carrier is received from the target base station; and the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, receiving the carrier identifier of the first target uplink carrier from the base station includes the following operation: an RRC message, which is the carrier identifier of the first target uplink carrier, is received from the target base station. 
     In an embodiment of the disclosure, receiving the carrier identifier of the first target uplink carrier from the base station includes the following operation: allocation information of the random access preamble is received from the target base station, the allocation information of the random access preamble including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, receiving the carrier identifier of the first target uplink carrier from the base station includes the following operation: handover command information from an original base station is received when the terminal device performs handover between the original base station and the target base station, the handover command information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, receiving the carrier identifier of the first target uplink carrier from the base station includes the following operation: reconfiguration information is received from the target base station after the target base station re-establishes an SCG or modifies the SCG, the reconfiguration information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station includes the following operations: an RRC message including a power threshold is received from the target base station; an RSRP of a current downlink carrier is detected; and the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers includes one SUL carrier and one non-SUL carrier; determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold includes the following operations: the non-SUL carrier is determined as the first target uplink carrier in response to the RSRP being greater than or equal to the power threshold; and the SUL carrier is determined as the first target uplink carrier in response to the RSRP being less than the power threshold. 
     In an embodiment of the disclosure, determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station includes the following operations: an RRC message including a quality threshold is received from the target base station; an RSRQ of the current downlink carrier is detected; and the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the RSRQ and the quality threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers includes one SUL carrier and one non-SUL carrier; determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRQ and the quality threshold includes the following operations: the non-SUL carrier is determined as the first target uplink carrier in response to the RSRQ being greater than or equal to the quality threshold; and the SUL carrier is determined as the first target uplink carrier in response to the RSRQ being less than the quality threshold. 
     In an embodiment of the disclosure, determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station includes the following operations: an RRC message including the power threshold and the quality threshold is received from the target base station; the RSRP and the RSRQ of the current downlink carrier is detected; and the first target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold as well as the RSRQ and the quality threshold. 
     In an embodiment of the disclosure, the plurality of uplink carriers includes one SUL carrier and one non-SUL carrier; determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station according to the RSRP and the power threshold as well as the RSRQ and the quality threshold includes the following operations: the non-SUL carrier is determined as the first target uplink carrier in response to the RSRP being greater than or equal to the power threshold, or in response to the RSRQ being greater than or equal to the quality threshold; and the SUL carrier is determined as first target uplink carrier in response to the RSRP being less than the power threshold and the RSRQ being less than the quality threshold. 
     In an embodiment of the disclosure, determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station includes the following operation: a carrier configured with a PUCCH among the plurality of uplink carriers is determined as the first target uplink carrier. 
     In an embodiment of the disclosure, determining the first target uplink carrier among the plurality of uplink carriers corresponding to the target base station includes the following operation: the first target uplink carrier is determined according to a random access resource included in each of the plurality of uplink carriers. 
     In an embodiment of the disclosure, the method further includes the following operations: random access response information is received from the target base station, the random access response information including the carrier identifier of a second target uplink carrier; the second target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station according to the carrier identifier of the second target uplink carrier; and scheduled transmission information is transmitted to the target base station using the second target uplink carrier. 
     In an embodiment of the disclosure, the method further includes the following operations: a third target uplink carrier is determined among the plurality of uplink carriers corresponding to the target base station if random access response information is not received from the target base station in a second preset period; and the random access preamble is transmitted to the target base station using the third target uplink carrier. 
     In an embodiment of the disclosure, transmitting the random access preamble to the target base station using the third target uplink carrier includes the following operations: a transmitting power, with which the random access preamble is transmitted to the target base station, is obtained using the first target uplink carrier; and the random access preamble is transmitted to the target base station on the third target uplink carrier with the transmitting power. 
     A non-transitory computer readable storage medium is provided in the embodiments of the disclosure. When instructions in the storage medium is executed by the processor of the device  90 , the device  90  can execute the above random access method at the base station side. The method includes the following operation. 
     Indication information is transmitted to a terminal device, the indication information being configured to indicate a first target uplink carrier to be determined, by the terminal device for transmitting a random access preamble, among a plurality of uplink carriers corresponding to the base station, and the plurality of uplink carriers including at least one SUL carrier. 
     In an embodiment of the disclosure, the method further includes the following operation: the first target uplink carrier configured for the terminal device to transmit the random access preamble is obtained among the plurality of uplink carriers; transmitting the indication information to the terminal device includes the following operation: a carrier identifier of the first target uplink carrier is transmitted to the terminal device to enable the terminal device to determine, according to the carrier identifier of the first target uplink carrier, the first target uplink carrier among the plurality of uplink carriers corresponding to the base station. 
     In an embodiment of the disclosure, obtaining, among the plurality of uplink carriers, the first target uplink carrier configured for the terminal device to transmit the random access preamble includes the following operation: the first target uplink carrier configured for the terminal device to transmit the random access preamble is obtained according to a random access resource included in each of the plurality of uplink carriers. 
     In an embodiment of the disclosure, transmitting the carrier identifier of the first target uplink carrier to the terminal device includes: an RRC message including the carrier identifier of the first target uplink carrier is transmitted to the terminal device. 
     In an embodiment of the disclosure, transmitting the carrier identifier of the first target uplink carrier to the terminal device includes: allocation information of the random access preamble is transmitted to the terminal device, the allocation information of the random access preamble including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, obtaining, among the plurality of uplink carriers, the first target uplink carrier configured for the terminal device to transmit the random access preamble includes the following operations: a handover request, which indicates that the terminal device performs handover from the original base station to the base station, is received from an original base station; the first target uplink carrier configured for the terminal device to transmit the random access preamble is obtained among the plurality of uplink carriers according to the handover request; transmitting the carrier identifier of the first target uplink carrier to the terminal device includes the following operation: handover response information is transmitted to the original base station, the handover response information including the carrier identifier of the first target uplink carrier to enable the original base station to transmit, to the terminal device, handover command information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, transmitting the carrier identifier of the first target uplink carrier to the terminal device includes the following operation: reconfiguration information is transmitted to the terminal device after the base station re-establishes an SCG or modifies the SCG, the reconfiguration information including the carrier identifier of the first target uplink carrier. 
     In an embodiment of the disclosure, transmitting the indication information to the terminal device includes the following operation: a power threshold is transmitted to the terminal device to enable the terminal device to determine, according to the power threshold and an RSRP of a current downlink carrier, the first target uplink carrier for transmitting the random access preamble among the plurality of uplink carriers corresponding to the base station. 
     In an embodiment of the disclosure, transmitting the indication information to the terminal device includes the following operation: a quality threshold is transmitted to the terminal device to enable the terminal device to determine, according to the quality threshold and an RSRQ of the current downlink carrier, the first target uplink carrier for transmitting the random access preamble among the plurality of uplink carriers corresponding to the base station. 
     In an embodiment of the disclosure, the method further includes: a second target uplink carrier configured for the terminal device to transmit scheduled transmission information is obtained among the plurality of uplink carriers according to the random access preamble transmitted by the terminal device; random access response information is transmitted to the terminal device, the random access response information including the carrier identifier of the second target uplink carrier. 
     Other implementation solutions of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the present disclosure. The present application is intended to cover any variations, uses, or adaptations of the present disclosure following the general principles thereof and including such departures from the present disclosure as come within known or customary practice in the art. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present disclosure being indicated by the following claims. 
     It will be appreciated that the present disclosure is not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. It is intended that the scope of the present disclosure only be limited by the appended claims.