METHOD AND APPARATUS OF COMMUNICATION

Abstract

The terms of this application provide a method and apparatus for communication. The method includes: Upon determining that a constant uplink LBT failure occurs in the first cell's BWP, a terminal-side device can indicate to a network-side device, by utilizing an uplink resource in a second cell, that the constant uplink LBT failure occurred in the first cell. According to the above method, the terminal-side device indicates, by utilizing the second cell in which no constant uplink LBT failure occurs, that the constant uplink LBT failure occurred in the first cell, so that the network-side device can more quickly determine that a constant uplink LBT failure occurred in the first cell. Therefore, the LBT failure can be recovered as soon as possible.

Description

COMMUNICATION METHOD AND APPARATUS CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Chinese Patent Application No. 202010091524.1, filed with the China National Intellectual Property Administration on February 13, 2020, entitled COMMUNICATION METHOD AND APPARATUS, which is incorporated herein by reference in its entirety. TECHNICAL FIELD This application relates to the field of wireless communication technologies, and in particular, to a communication method and apparatus. BACKGROUND OF THE INVENTION As mobile data service volumes continually increase, spectrum resources are increasingly strained. Service transmission performed using only a licensed spectrum resource cannot meet a service volume requirement. Therefore, service transmission performed in unlicensed spectrum is considered in a Long Term Evolution (LTE) system, a New Radio (NR) system, and the like. Unlicensed spectrum is spectrum that can be shared by many different air interface technologies, for example, a wireless local area network compliant with an Institute of Electrical and Electronics Engineers (IEEE) 802.11 protocol and LTE Licensed Assisted Access (LAA).Therefore, to avoid interference, before transmitting services using unlicensed spectrum, a terminal-side device can compete for a channel in the unlicensed spectrum using a channel access procedure. If channel access is successful, data transmission can be carried out using the unlicensed spectrum. If channel access fails, data transmission cannot be carried out. When the terminal-side device experiences a consistent uplink listen before talk (LBT) failure on an active bandwidth part (BWP) in a serving cell, the terminal-side device may trigger reporting of an LBT failure medium access control (MAC) control element (CE) to a network-side device. The LBT failure MAC CE is used to indicate whether the consistent uplink LBT failure occurs in the serving cell. The LBT Failed MAC CE cannot be sent in the serving cell where the persistent uplink LBT Failed MAC CE is already occurring. Therefore, how to send the LBT Failed MAC CE is an urgent problem to be solved. BRIEF DESCRIPTION OF THE INVENTION An objective of the implementations of this application is to provide a method and communication apparatus for solving a problem of how a terminal-side device sends an LBT failure MAC CE. According to a first aspect, this application provides a communication method, which includes: A terminal-side device determines that a persistent uplink LBT listen-before-talk failure occurs in a first BWP bandwidth portion of a first cell. The terminal-side device sends first information to a network-side device when utilizing an uplink resource in a second cell. The first information is used to indicate that the terminal-side device experiences the persistent uplink LBT failure in the first cell, and the second cell is a cell in which a persistent uplink LBT failure does not occur. According to the above method, when the constant uplink LBT listen-before-talk failure is experienced in the first cell, the terminal-side device may send the first information through the second cell, so that the network-side device can more quickly determine, based on the first information, that the LBT failure occurs in the first cell, and the LBT failure can be recovered as soon as possible. In a possible implementation, the method further includes: The terminal-side device starts a first timer. The timing duration of the first timer is the first duration. When the first timer expires, the terminal-side device switches to a second BWP of the first cell, if the terminal-side device does not receive, from the network-side device, a second information in response to the first information. The second BWP includes a resource for performing a random access procedure. The second information is DCI downlink control information used to program the terminal-side device to perform the BWP switchover. The terminal-side device performs the random access procedure in the second BWP by using the resource for performing the random access procedure. In the above method, the first timer is started, so that the terminal-side device cannot frequently perform BWP switching. In a possible implementation, the terminal-side device sending the first information when utilizing an uplink resource in a second cell includes: The terminal-side device sending the first information when utilizing the uplink resource in the second cell when the terminal-side device determines that a number of times of sending the first information is less than N. N is an integer nAcnon / zznz / q / υιλι greater than 1. In a possible implementation, the method further includes: The terminal-side device switches to a second BWP of the first cell when the terminal-side device determines that the number of times of sending the first information is not less than N. N is an integer greater than 1. The second BWP includes a resource for performing a random access procedure. The terminal-side device performs the random access procedure in the second BWP by using the resource for performing the random access procedure. In a possible implementation, the method further includes: When the random access procedure is a two-step random access procedure, the terminal-side device sends the first information by using a physical uplink shared channel resource PUSCH determined based on a preamble and a physical random access channel occasion PRACH corresponding to the preamble, in the two-step random access procedure. Alternatively, when the random access procedure is a four-step random access procedure, the terminal-side device sends the first information by using an uplink resource allocated by using a random access response message RAR in the four-step random access procedure. In a possible implementation, the terminal-side device sending the first information upon utilizing an uplink resource in a second cell includes: The terminal-side device switches to a second BWP of the first cell. The second BWP includes a resource for performing a random access procedure. The terminal-side device initiates a two-step random access procedure in the second BWP upon utilizing the resource for performing the random access procedure.The terminal-side device sends the first information when utilizing the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of a PUSCH physical uplink shared channel resource that is determined based on a preamble and a PRACH physical random access channel occasion corresponding to the preamble in the two-step random access procedure. Alternatively, the terminal-side device initiates a four-step random access procedure in the second BWP when utilizing the resource to perform the random access procedure.The terminal-side device sends the first information when using the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of an uplink resource allocated by using a random access response message RAR in the four-step random access procedure nAcnon / zznz / q / υιλι. In one possible implementation, the first cell is a primary cell or a primary secondary cell, and the second cell is a secondary cell. According to a second aspect, this application provides a communication method, which includes: A terminal-side device determining that a constant uplink LBT listen-before-talk failure occurs in a first BWP bandwidth portion of a first cell. The first cell is a primary cell or a primary secondary cell. A second cell is a secondary cell. The second cell is a cell in which no constant uplink LBT failure occurs and includes an available uplink resource. The terminal-side device switches to a second BWP of the first cell and sends first information on the second BWP of the first cell to the first cell and the second cell. The first information is used to indicate that the terminal-side device experiences the constant uplink LBT failure in the first cell. In a possible implementation, the second BWP includes a resource for performing a random access procedure. The terminal-side device sends the first information in the second BWP of the first cell in the first cell and the second cell includes: The terminal-side device performs the random access procedure in the second BWP by using the resource for performing the random access procedure. When the random access procedure is a two-step random access procedure, the terminal-side device sends the first information by using a PUSCH physical uplink shared channel resource corresponding to a preamble in the two-step random access procedure.Alternatively, when the random access procedure is a four-step random access procedure, the terminal-side device sends the first information by using an allocated uplink resource by using a random access response message RAR in the four-step random access procedure. According to a third aspect, this application provides a communication method, including: A terminal-side device determining that a constant uplink LBT listen-before-talk failure occurs in a fourth BWP bandwidth portion of a third cell. Before generating the third information, the terminal-side device cancels a constant uplink LBT failure state of the third cell if the terminal-side device determines to switch to a fifth BWP of the third cell. The third information is used to indicate that the terminal-side device does not experience the constant uplink LBT failure in the third cell. nAcnon / zznz / q / υιλι In the above method, the terminal-side device experiences the constant uplink LBT failure at the fourth BWP of the third cell. If it switches to the fifth BWP of the third cell, the terminal-side device can cancel the constant uplink LBT failure state of the third cell, to avoid a case where a network-side device incorrectly understands the state of the third cell upon receiving an LBT failure MAC CE indicating that the constant uplink LBT failure occurs in the third cell. In one possible implementation, the determination to switch to a fifth BWP of the third cell includes: The terminal-side device receives DCI downlink control information from the network-side device. The DCI is used to indicate that the terminal-side device switches to the fifth BWP. According to a fourth aspect, this application further provides a communication apparatus. The communication apparatus has a function of implementing any method provided in any of the first aspect through the third aspect. The communication apparatus may be implemented by hardware, or it may be implemented by hardware running corresponding software. The hardware or software includes one or more units or units corresponding to the above function. In one possible implementation, the communication apparatus includes a processor. The processor is configured to assist the communication apparatus in performing a corresponding function of the terminal-side device in the above method. The communication apparatus may further include a memory. The memory may be coupled to the processor, and the memory stores program instructions and data necessary for the communication apparatus. Optionally, the communication apparatus further includes a communication interface. The communication interface is configured to support communication between the communication apparatus and a device such as a network-side device. In one possible implementation, the communication device includes corresponding function units, respectively configured to implement the steps in the above method. The function may be implemented by hardware, or it may be implemented by hardware running corresponding software. The hardware or software includes one or more units corresponding to the above function. In one possible implementation, a communication apparatus structure includes a processing unit and a communication unit. The units may perform corresponding functions in the example of the above method. For further details, see the descriptions in the method provided in the first aspect or the third aspect. Details are not described again here. nAcnon / zznz / q / υιλι According to an eighth aspect, this application provides a communication apparatus. The communication apparatus includes a processor. When the processor executes a computer program or instructions in a memory, the method according to any of the first aspect to the third aspect is performed. According to a sixth aspect, this application provides a communication apparatus. The communication apparatus includes a processor and a memory. The memory is configured to store a computer program or instructions. The processor is configured to execute the computer program or instructions stored in the memory, to enable the communication apparatus to perform the corresponding method according to any of the first aspect to the third aspect. According to a seventh aspect, this application provides a communication apparatus. The communication apparatus includes a processor, a memory, and a transceiver. The transceiver is configured to receive a signal or send a signal. The memory is configured to store a computer program or instructions. The processor is configured to call the computer program or instructions from the memory, to perform the method according to any of the first aspect to the third aspect. According to an eighth aspect, this application provides a communication apparatus. The communication apparatus includes a processor and an interface circuit. The interface circuit is configured to: receive code instructions and transmit the code instructions to the processor. The processor executes the code instructions to perform the corresponding method according to any of the first aspect to the third aspect. According to a ninth aspect, this application provides a computer-readable storage medium. The computer-readable storage medium is configured to store a computer program or instructions. When a computer reads and executes the computer program or instructions, the method according to any of the first aspect through the third aspect is implemented. According to a tenth aspect, this application provides a computer program product including instructions. When a computer reads and executes the computer program product, the method according to any one of the first aspect to the third aspect is implemented. According to an eleventh aspect, this application provides a chip. The chip includes a processor. The processor is coupled to a memory and configured to execute a computer program or instructions stored in the memory. When the processor executes the computer program or instructions, the method according to any of the first aspect to the third aspect is implemented. According to a twelfth aspect, this application provides a chip. The chip is connected to a memory and is configured to read and execute a software program stored in the memory, for implementing the method in any of the first aspect to the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic diagram of a dual connectivity architecture applicable to one embodiment of this application. FIGURE 2 is a schematic flow diagram of a four-step random access procedure. FIGURE 3 is a schematic flow diagram of a two-step random access procedure. FIGURE 4 is a schematic flow diagram of a communication method according to one embodiment of this application. FIGURE 5 is a schematic diagram of a structure of a MAC CE according to an embodiment of this application. FIGURE 6 is a schematic flow diagram of a communication method according to an embodiment of this application. FIGURE 7 is a schematic flow diagram of a communication method according to one embodiment of this application. FIGURE 8 is a schematic diagram of a time sequence according to one embodiment of this application. FIGURE 9 is a schematic diagram of another structure of a MAC CE according to an embodiment of this application. FIGURE 10 is a schematic diagram of a structure of a communication apparatus according to an embodiment of this application. FIGURE 11 is a schematic diagram of a structure of a communication apparatus according to an embodiment of this application. DETAILED DESCRIPTION OF THE MODALITIES The following describes in detail the embodiments of the present application with reference to the drawings accompanying this specification. The technical solutions in the embodiments of this application may be applied to various communication systems, for example, a fifth-generation (5G) mobile communication system (e.g., New Radio (NR)) and a Long Term Evolution (LTE) system. The LTE system may include an LTE frequency division duplexing (FDD) system, an LTE time division duplexing (TDD) system, and the like. This is not limited herein. nAcnon / zznz / q / υιλι In embodiments of this application, a plurality of means two or more. In view of this, in embodiments of this application, a plurality of may alternatively be understood as at least two. At least one may be understood as one or more, for example, one, two, or more. For example, including at least one means including one, two, or more, and does not limit which elements are included. For example, if at least one of A, B, and C is included, then A, B, C, A and B, A and C, B and C, or A, B and C may be included. Similarly, understanding a description such as at least one type is similar. And / or describes an association relationship between associated objects and indicates that three relationships may exist. For example, A and / or B may indicate the following three cases: Only A exists, both A and B exist, and only B exists. In addition, the character / generally indicates an or relationship between the associated objects, unless otherwise specified. A terminal-side device in embodiments of this application may be a device having a wireless transceiver function or a chip that may be arranged in any device, or may be referred to as a user equipment (UE), an access terminal, a subscriber unit, a subscriber station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a wireless communication device, a user agent, or a user apparatus.The terminal-side device in embodiments of this application may be a mobile phone, a tablet computer, a computer having a wireless transceiver function, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, or the like. A network-side device may be an evolved NodeB (eNB) in the LTE system, a next generation NodeB (gNB) in the NR system, or the like.Embodiments of this application may be applied to a network-side device and a terminal-side device that support a single-base-station carrier aggregation (CA) technology, and to a network-side device and a terminal-side device that support a cross-base-station carrier aggregation technology, such as a dual-connectivity (DC) technology. The network-side device and the terminal-side device may aggregate at least two component carriers (CCs) together to support a wider transmission bandwidth. One of the CCs may correspond to an independent cell. The single-base-station carrier aggregation technology is generally referred to as carrier aggregation technology for short.Unless otherwise specified, the carrier aggregation technology below is the carrier aggregation technology of a single base station. It should be noted that carrier aggregation technology and dual connectivity technology have at least the following differences: 1. In dual connectivity, data streams are separated and combined at a packet data convergence protocol (PDCP) layer. The data streams are transmitted simultaneously to a user via multiple base stations. In carrier aggregation, the data streams are separated and combined at a medium access control (MAC) layer. 2. Dual connectivity is the addition of different stations, typically a macro base station and a micro base station. The macro base station and micro base station are connected to each other via an X2 interface. Carrier aggregation is the addition of different CCs within a single station. In a dual connectivity scenario, a master cell group (MCG) may be included. A group of cells other than the MCG may be referred to as a secondary cell group (SCG). For further details, see FIGURE 1. In FIGURE 1, a terminal-side device 104 separately establishes connections with a network-side device 102 and a network-side device 106. For the terminal-side device 104, a cell group on the network-side device 102 may be an MCG, and a cell group on the network-side device 106 may be an SCG. There can be many cells in the MCG. One of the cells is used to initiate the initial access. The cell is called the primary cell (PCell). Another cell is called the secondary cell (SCell). The PCell in the MCG and the SCell in the MCG are aggregated using carrier aggregation technology. Therefore, there is also one more primary cell in the SCG, and the cell may be called the primary secondary cell (PSCell). Another cell in the SCG is called the secondary cell. The PSCell in the SCG and the SCell in the SCG are also aggregated using CA technology. For ease of description, a term special cell (sPCell) is defined in a current protocol. For the dual-connectivity scenario, the term special cell is the PCell in the MCG or the PSCell in the SCG. Otherwise, the term special cell is PCell. When a terminal-side device accesses a cell, in addition to an initial BWP, a network-side device can configure a dedicated BWP for the terminal-side device and can configure up to four dedicated BWPs. The network-side device can activate one of the BWPs. A terminal-side device has only one active BWP in a cell at a time. The terminal-side device can transmit data on the active BWP. In this embodiment of this application, the network-side device configures one or more BWPs for the terminal-side device in an unlicensed spectrum cell and activates a BWP on the configured BWPs. The terminal-side device may communicate with the network-side device using unlicensed spectrum. Before the terminal-side device communicates with the network-side device using unlicensed spectrum, the terminal-side device performs an uplink LBT to compete for a channel. It should be noted that LBT may alternatively be referred to as a channel access procedure. For ease of description, channel access procedures are collectively referred to as LBT below. There are two types of LBT. Type 1: Fixed-duration LBT. If the energy of a signal detected by the end-side device on a channel within the fixed duration is less than a preset threshold, the channel is considered idle. In this case, the end-side device may occupy the channel. Otherwise, the end-side device must compete for the channel again. Therefore, for Type 1 LBT, if the signal energy detected by the end-to-end device on the channel within the fixed duration is greater than the preset threshold, the channel is considered busy. In this case, the end-to-end device may determine that the LBT has failed. The end-to-end device may occupy a channel for data transmission only when it determines that the channel is idle. Type 2: Power detection based on a backoff mechanism. The end-side device randomly selects a value A, where A is an integer greater than 0. Before a data transmission start point, the end-side device considers a channel to be idle only after detecting at least A idle intervals for power detection. Otherwise, the end-side device considers the channel to be busy. The data transmission start point may be a data transmission start time of the data to be transmitted from the end-side device. Therefore, for Type 2 LBT, if the terminal-side device has not detected at least A idle slots for power detection before the data transmission start point, the terminal-side device may determine that the LBT fails. For example, data is transmitted in one slot. The slot includes 14 symbols (which are symbols 0 to 13). Assuming that the terminal-side device starts transmitting data from symbol 0, if the terminal-side device has not detected at least A idle slots for power detection at a start time of symbol 0, the terminal-side device may determine that the LBT fails. When the terminal-side device performs an uplink LBT on the active BWP, the terminal-side device determines that each time an uplink LBT failure occurs on the BWP, the terminal-side device may perform the following operations: 1. Increment a count value of an LBT failure counter (LBT_FAIL_COUNTER) by 1, where an initial value of the counter is 0. 2. Start or reset a timer (the timer may be IbtFailureDetectionTimer defined in 3GPP specifications), where the timing duration of the timer may be the duration configured by the network-side device. Before the timer expires, if the LBT failure counter count value reaches a threshold, the end-side device may determine that a consistent uplink LBT failure has occurred on the active BWP. When the timer expires, the end-side device may reset the counter count value to 0. In this embodiment of this application, upon determining that a persistent uplink LBT failure occurs in a serving cell, the terminal-side device may send an LBT failure MAC CE to the network-side device. Therefore, this embodiment of this application provides a method for sending an LBT failure MAC CE. The following provides detailed descriptions. The method provided in this embodiment of this application relates to a two-step random access procedure and a four-step random access procedure, which are described separately below. It should be noted that the four-step random access procedure includes a contention-based four-step random access procedure and a non-contention-based four-step random access procedure. This embodiment of this application refers to the contention-based four-step random access procedure. Unless otherwise specified, the four-step random access procedure described in this embodiment of this application is the contention-based four-step random access procedure. As shown in FIGURE 2, the four-step contention-based random access procedure includes the following steps. Step 210: A terminal-side device sends a preamble to a network-side device. The preamble is also called message 1 (msg 1) of the random access procedure. If the network-side device successfully detects the preamble sent by the terminal-side nRcnon / zznz / q / υιλι device, the network-side device sends a random access response (RAR) message corresponding to the preamble. Step 220: The network-side device sends the RAR message to the terminal-side device. The RAR message may also be referred to as message 2 (msg 2). The RAR message includes an uplink timing advance, an uplink grant (UL grant) allocated for transmission of message 3 (msg 3), a temporary cell radio network temporary identifier (temporary C-RNTI) assigned by the network-side device, and the like. A physical downlink control channel (PDCCH) scheduling the RAR message is encrypted using a random access radio network temporary identifier (RA-RNTI). After sending the preamble, the end-side device may monitor a corresponding PDCCH within a RAR response window based on a RARNTI value corresponding to the preamble. If a preamble corresponding to a preamble index carried in the RAR message obtained by the end-side device using the monitored PDCCH is consistent with the preamble sent by message 1, the end-side device stops monitoring the RAR message. Therefore, if the terminal-side device does not receive the RAR message within a RAR time window, or no preamble corresponding to the preamble index in the received RAR message matches the preamble sent by the terminal-side device, the terminal-side device considers that the random access procedure fails. Step 230: The terminal-side device sends a scheduled transmission message, that is, message 3, to the network-side device. The terminal-side device sends message 3 to the network-side device over a physical uplink shared channel (PUSCH) based on the uplink grant and uplink timing advance information in message 2. Step 240: The terminal-side device receives a dispute resolution message, namely, message 4, sent by the network-side device. Contention occurs when multiple end-side devices use the same preamble to initiate random access. At most one end-side device among the end-side devices contending for the same resource can succeed in accessing it. In this case, the network-side device sends the nRcnon / zznz / q / uyl contention resolution message to the end-side device via a PDSCH. Specifically, after sending message 3, the terminal-side device starts a contention resolution timer (mac-Contention Resolution Timer) and monitors the PDCCH using the temporary C-RNTI indicated in the RAR message or a C-RNTI preconfigured by the network-side device. If the terminal-side device receives the contention resolution message sent by the network-side device to the terminal-side device before the contention resolution timer expires, the terminal-side device judges that the random access procedure succeeds. Otherwise, the terminal-side device determines that the random access procedure fails. As shown in FIGURE 3, the two-step random access procedure includes the following steps. Step 310: A terminal-side device sends a message A (message A, msg A) to a network-side device. Specifically, msg A includes a random access signal and payload data. The payload data is carried using a PUSCH resource. The PUSCH resource is a physical uplink shared channel (PUSCH) resource determined based on a preamble and a physical random access channel (PRACH) occasion corresponding to the preamble. The random access signal may include at least one of a preamble and a demodulation reference signal (DMRS). The random access signal is used by the network-side device to receive the payload data. For example, based on the random access signal, a transmission boundary of the payload data (e.g., a start position and an end position of a slot for transmitting the payload data) may be determined, the payload data may be demodulated, and the like. The payload data may be at least one of control plane data and user plane data. The payload data may include, but is not limited to, one or more of an RRC connection request, a terminal-side device identifier, a scheduling request, a buffer status report (BSR), and service data. Optionally, the terminal-side device identifier may be a C-RNTI, a serving-temporary mobile subscriber identity (sTMSI), a resumedentity of the terminal-side device in an idle state, or the like. A specific identifier to be carried depends on different random access trigger events. This is not limited in this embodiment of this application. It should be noted that the terminal-side device identifier may be carried entirely in the payload data, or may be partially carried in the payload data and partially carried in the random access signal. Step 320: The network-side device sends a message B (message B, msg B) to the terminal-side device. Specifically, msg B is used to carry a response message for the random access signal and the payload data in msg A. The response message may include at least one of the following: a temporary C-RNTI, a timing advance command, an uplink grant, a contention resolution identity, and the like. The contention resolution identity may be part or all of the payload data. A network architecture and service scenario described in the embodiments of this application are intended to more clearly describe the technical solutions in the embodiments of this application, but they do not constitute any limitation on the technical solutions provided in the embodiments of this application. One of ordinary skill in the art would recognize that, with the evolution of network architecture and the emergence of new service scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems. The modalities of this application mainly provide the following solutions: 1. When a persistent uplink LBT failure occurs in a first cell (e.g., the first cell is an SpCell), a terminal-side device may send an LBT Failure MAC CE. The LBT Failure MAC CE is used to indicate that the persistent uplink LBT failure occurs in the first cell. During the initiation of a random access procedure, the terminal-side device may send the LBT Failure MAC CE in a BWP to which the terminal-side device switches. 2. After sending an LBT fail MAC CE, a terminal-side device can recover from an uplink LBT failure in a first cell without BWP switching. When a persistent uplink LBT failure occurs in the first cell (for example, the first cell is an SpCell), the terminal-side device may send the LBT Failure MAC CE. The LBT Failure MAC CE is used to indicate that the persistent uplink LBT failure occurs in the first cell. The terminal-side device may send the LBT Failure MAC CE by utilizing a CG / DG grant from a second cell (for example, the second cell may be an SCell). The second cell is a cell in which a persistent uplink LBT failure does not occur. It should be noted that after sending the LBT fail MAC CE, the terminal side device nAcnon / zznz / q / uιλι cannot perform BWP switching before receiving DCI which is from a network side device and indicates to perform BWP switching. 3. After sending an LBT Fail MAC CE, a terminal-side device may start a timer. Before the timer expires, the terminal-side device waits for the DCI from a network-side device, but does not perform BWP switching. The DCI instructs the terminal-side device to perform BWP switching. When the timer expires, if the terminal-side device does not receive the DCI instructing the terminal-side device to perform BWP switching, the terminal-side device may perform BWP switching and initiate a random access procedure. In this case, if the terminal-side device initiates a four-step random access procedure, the LBT fail MAC CE may be carried in msg 3. If the terminal-side device initiates a two-step random access procedure, the LBT fail MAC CE may be carried in msg A. 4. When a terminal-side device experiences a constant uplink LBT failure in a first cell (e.g., the first cell is an SpCell), it performs BWP switchover and initiates a random access procedure in a switched-to BWP, and in the random access procedure, if a second cell (e.g., the second cell may be an SCell) in which a constant uplink LBT failure does not occur has an available uplink resource, and a start time of the available uplink resource in the second cell is earlier than a sending time of payload data of an A msg in a two-step random access procedure, or earlier than a start time of an uplink resource indicated by a RAR message in a four-step random access procedure, the terminal-side device may send an LBT failure MAC CE in the first cell.In this case, the terminal-side device does not send the LBT failed MAC CE during the random access procedure. However, because the BWP switchover has been initiated, the terminal-side device can notify a network-side device of the BWP to which it is switching only after the BWP switchover is complete. 5. When a constant uplink LBT failure is experienced in a third cell (for example, the third cell is an SCell), before generating an LBT Failure MAC CE used to indicate that a constant uplink LBT failure occurs, a terminal-side device cancels a constant uplink LBT failure state of the third cell if the terminal-side device receives the DCI indicating that the terminal-side device performs BWP switching. With reference to the foregoing descriptions, FIGURE 4 is a schematic flow diagram of a communication method according to an embodiment of this application. nRcnon / zznz / q / υιλι In the method procedure shown in FIG. 4, both a first cell and a second cell may serve a terminal-side device. When the method procedure shown in FIG. 4 is applied to a scenario in which a network-side device performs communication using a carrier aggregation technology, the first cell may be a primary cell and the second cell may be a secondary cell. When the method procedure shown in FIG. 4 is applied to a scenario in which the network-side device performs communication using a dual-connectivity technology, the first cell may be a primary cell and the second cell may be a secondary cell that is in the same master cell group as the first cell.Alternatively, the first cell may be a primary child cell, and the second cell may be a child cell that is in the same child cell group as the first cell. See FIGURE 4. The method includes the following steps. Step 401: The terminal-side device determines that a constant uplink LBT failure occurs at a first BWP of the first cell. It should be noted that the first BWP is a BWP triggered by the network-side device for the terminal-side device in the first cell. The specific manner in which the terminal-side device experiences the constant uplink LBT failure is not limited in this embodiment of this application. For example, see the descriptions above. Details are not described again here. Step 402: The terminal-side device sends the first information to the network-side device using an uplink resource in the second cell. The first information is used to indicate that the terminal-side device experiences constant uplink LBT failure in the first cell. Furthermore, the second cell is a cell in which no constant uplink LBT failure occurs. It should be noted that if the second cell is a cell in which no constant uplink LBT failure occurs, this may mean that when sending the first information, the terminal-side device determines that no constant uplink LBT failure occurs in the second cell, or it may mean that when determining the uplink resource used to send the first information, the terminal-side device determines that no constant uplink LBT failure occurs in the second cell. It should be noted that, in this embodiment of this application, the uplink resource in the second cell is an uplink resource used by the terminal-side device for a new transmission. For example, the uplink resource in the second cell may include, but is not limited to, one or more of the following: nAcnon / zznz / q / υιλι a configured grant resource; and a resource scheduled over a physical downlink control channel (PDCCH) encrypted using a cell radio network temporary identity (C-RNTI) of the terminal-side device. The terminal-side device may send uplink data on configured grant uplink resources without dynamic scheduling by the network-side device of the configured grant resources that may be used for uplink transmission. The resources include, but are not limited to, configured grant type 1 and configured grant type 2 uplink resources in a new radio-unlicensed (NR-U) system. A first configuration form is configured grant type 1: The network-side device may pre-configure, in a semi-static resource allocation manner, a resource required by the terminal-side device for uplink transmission, i.e., the configured grant resource, which may also be referred to as the configured UpLink grant resource. The resource is referred to as the configured grant resource below. It should be noted that the configured grant resource may appear periodically, and the terminal-side device does not need to first obtain an uplink grant each time before sending the uplink transmission. For example, the network-side device may configure the configured grant resource for uplink transmission by using radio resource control (RRC) signaling.RRC signaling may also include a configured grant resource periodicity, so that the terminal-side device can transmit data about the configured grant resource. A second configuration is configured grant type 2: The network-side device may indicate certain information about the configured grant resource using RRC signaling, for example, a periodicity for the configured grant resource. In addition, the network-side device may additionally indicate the configured grant resource using physical layer signaling. Physical layer signaling is also used to activate the configured grant resource so that the terminal-side device can transmit data about the configured grant resource. It should be noted that the naming of the first configuration form is not limited to the configured grant type 1. The first configuration form may also have another name. This is not limited in this embodiment of this application. Similarly, the naming of the second configuration form is not limited to the configured grant type nAcnon / zznz / q / uyl 2. The second configuration form may have another name. A communication system to which the first configuration form and the second configuration form are applicable is not limited in this embodiment of this application. The communication system may be an LTE communication system, a 5G communication system, or another communication system. In this embodiment of this application, a specific implementation of the first information is not limited. In a possible implementation, the first information is a MAC CE, for example, an LBT failure MAC CE. For example, FIG. 5 is a schematic diagram of a structure of a MAC CE according to an embodiment of this application. The MAC CE shown in FIG. 5 includes a plurality of cell identifier fields. For example, FIG. 5 includes 31 cell identifier fields: C1 to C31. When a bit value corresponding to a cell identifier field is a first value, it indicates that the terminal-side device experiences the constant uplink LBT failure in a cell corresponding to the cell identifier field.When a bit value corresponding to a cell identifier field is a second value, it indicates that the terminal-side device does not experience the persistent uplink LBT failure in a cell corresponding to the cell identifier field. The specific values ​​of the first value and the second value are unlimited. For example, the first value is 1 and the second value is 0. The MAC CE shown in FIG. 5 may further include a primary cell field, which is represented by P in FIG. 5. In actual implementation, the primary cell field may be represented otherwise. This is not limited in this embodiment of this application. The primary cell field is used to indicate whether the terminal-side device experiences the constant uplink LBT failure in a primary cell. Similarly, when a bit value corresponding to the primary cell field is a first value, it indicates that the terminal-side device experiences the constant uplink LBT failure in the primary cell. When a bit value corresponding to the primary cell field is a second value, it indicates that the terminal-side device does not experience the constant uplink LBT failure in the primary cell. The specific values ​​of the first value and the second value are not limited.For example, the first value is 1 and the second value is 0. The MAC CE shown in FIGURE 5 may also include another field, for example, a reserved (R) field. The examples are not described individually here. With reference to the above descriptions, when the first information is an LBT fail MAC CE, and when the terminal-side device performs logical channel priority setting based on the uplink resource of the second cell, where nAcnon / zznz / q / υιλι an obtained priority setting result indicates that the uplink resource in the second cell may include the LBT fail MAC CE and a subheader of the LBT fail MAC CE, the terminal-side device may send the first information about the uplink resource of the second cell. In this embodiment of this application, the terminal-side device may also perform BWP switching. BWP switching means that an active BWP is switched from a current BWP to another BWP. After performing BWP switching, the terminal-side device stops using the BWP it is switching from and starts using the BWP it is switching to. The details are described separately below. Implementation 1: Stage 1: A terminal-side device determines that a constant uplink LBT failure occurs at a first BWP of a first cell. Stage 2: The terminal-side device sends the first information when using an uplink resource in a second cell and may initiate a first timed The timing duration of the first timer is the first duration. The first duration may be configured by a network-side device, or it may be determined independently by the terminal-side device, or it may be a duration specified in a communication protocol, or it may be determined in another way. This is not limited to this embodiment of this application. In this application mode, timing begins when the first timer starts. When the duration of the first timer is the first duration, the timing of the first timer ends. In this case, the first timer can be considered to have expired. Step 3: After the first timer starts, the terminal-side device can perform BWP switching in any of the following cases. Case 1: After the first timer starts, if the second information is received from the network-side device during the execution of the first timer, the terminal-side device can switch to a third BWP indicated by the second information and stop the first timer. The second information is downlink control information (DCI) used to program the terminal-side device to perform BWP switching. The second information is used to indicate that the terminal-side device switches to the third BWP. Case 2: When the first timer expires, to be specific, the terminal-side device does not receive, from the network-side device within the first duration from the start of the first timer to the end of the first timer, the second information in response to the first information, the terminal-side device may nAcnon / zznz / q / uyl actively perform BWP switching, for example, switch a second BWP of the first cell. It should be noted that during the execution of the first timer, the terminal-side device does not actively perform BWP switching on the first cell, but performs BWP switching only when it receives the second information from the network-side device. It should be noted that the second and third BWPs may be the same BWP or different BWPs. This is not limited to this application modality. Step 4: The terminal-side device completes the BWP switchover, to recover from the constant uplink LBT failure. An example is used below where the terminal-side device switches to the second BWP for descriptions. In this embodiment of this request, the second BWP may include at least one resource for performing a random access procedure and a scheduling request (SR) resource. The resource for performing the random access procedure may include at least one resource for performing a two-step random access procedure and a resource for performing a four-step random access procedure. The resource for performing the two-step random access procedure includes a PRACH resource for sending a preamble and a PUSCH resource determined based on the preamble and a PRACH occasion corresponding to the preamble. The terminal-side device can recover from the constant uplink LBT failure by performing the random access procedure or an SR procedure on the second BWP. In a first possible implementation, the terminal-side device may perform, in the second BWP, the random access procedure by using the resource for performing the random access procedure included in the second BWP. It should be noted that the random access procedure performed by the terminal-side device in the second BWP may be a two-step random access procedure, or it may be a four-step random access procedure. For example, when the second BWP includes only the resource for performing the two-step random access procedure, the terminal-side device may perform the two-step random access procedure in the second BWP. When the second BWP includes only the resource for performing the four-step random access procedure, the terminal-side device may perform the four-step random access procedure in the second BWP.When the second BWP includes the two-step random access procedure resource and the four-step random access procedure resource, the terminal-side device nRcnon / zznz / q / uylii determines, based on a received power reference signal (RSRP), whether to initiate the two-step random access procedure or the four-step random access procedure. Upon determining that the received power of the reference signal is greater than a threshold, the terminal-side device initiates the two-step random access procedure. Upon determining that the received power of the reference signal is less than or equal to the threshold, the terminal-side device initiates the four-step random access procedure. By way of example but not limitation, the reference signal may be a downlink path loss reference signal. In addition, the terminal-side device may send the first information to the network-side device in the random access procedure. Case 1: When the random access procedure performed by the terminal-side device in the second BWP is the two-step random access procedure, the terminal-side device can send the first information by using the PUSCH resource which is determined based on the preamble and the PRACH occasion corresponding to the preamble in the two-step random access procedure. Specifically, the PUSCH resource determined based on the preamble and the PRACH opportunity corresponding to the preamble can be used to send payload data of an A message in the two-step random access procedure. Therefore, the terminal-side device can send the first piece of information using the A message in the two-step random access procedure. See the two-step random access procedure shown in FIGURE 3. Case 2: When the random access procedure performed by the terminal-side device in the second BWP is the four-step random access procedure, the terminal-side device can send the first information by using an uplink resource allocated by using a random access response (RAR) message in the four-step random access procedure. It should be noted that in the four-step random access procedure, the RAR message may also be referred to as message 2. The RAR message may include information such as an uplink timing advance and an uplink grant (msg 3) allocated for message 3. The uplink grant in the RAR message is used to allocate an uplink resource for message 3. The terminal-side device may send message 3 by using the uplink resource allocated by using the uplink grant in the RAR message. Therefore, the terminal-side device may send the first information using message 3 in the four-step random access procedure. nAcnon / zznz / q / υιλι In a second possible implementation, the second BWP to which the terminal-side device switches may include the scheduling request (SR) resource. The terminal-side device may perform, in the second BWP, a resource scheduling request procedure by using the scheduling request resource included in the second BWP. In addition, in the resource scheduling request procedure, the terminal-side device may send an SR to request an uplink resource and send the first information when using the requested uplink resource by using the SR. It should be noted that, when the terminal-side device forwards, using message 3 in the four-step random access procedure, message A in the two-step random access procedure, or the requested uplink resource by using SR, the first information that is sent via the second cell, in a possible implementation, the terminal-side device stores a state of a serving cell included in the first information sent via the second cell, and regenerates the first information. Implementation 2 Step 1; A terminal-side device determines that a constant uplink LBT failure occurs at a first BWP of a first cell. Step 2: The terminal-side device may send the first information a plurality of times by utilizing an uplink resource in a second cell. Each time before sending the first piece of information in the second cell, the terminal-side device may determine a number of times the first piece of information has been sent. For example, the terminal-side device may maintain a counter. Each time the first piece of information is sent in the second cell, the counter's count value is incremented by 1. Each time before sending the first piece of information in the second cell, the terminal-side device first determines whether the counter value reaches N. If the terminal-side device determines that the number of times the first information is sent is less than N, the terminal-side device determines to send the first information by using the uplink resource in the second cell. When the terminal-side device determines that the number of times the first information is sent is not less than N, the terminal-side device determines not to send the first information when utilizing the uplink resource in the second cell. The terminal-side device may actively perform BWP switching, for example, switching to a second BWP of the first cell. N is a maximum number of times that the terminal-side device sends the first information when using the uplink resource in the second cell, and may be set by a network-side device when using RRC signaling, may be independently determined by the terminal-side device, may be agreed upon in a communication protocol, or may be determined in some other way. This is not limited in this embodiment of this application. Stage 3: The terminal-side device can perform BWP switching in any of the following cases. It should be noted that the sequence of Stage 2 and Stage 3 is not limited. If the terminal-side device receives a second piece of information before Stage 2, the BWP switchover can be performed first. Case 1: When the number of times of sending the first information is not less than N, the terminal-side device can actively switch to the second BWP of the first cell. Case 2: When the number of times the first information is sent is less than N, if the terminal-side device receives the second information from the network-side device, the terminal-side device can switch to a third BWP indicated by the second information. The second information is used to indicate the third BWP to which the terminal-side device switches. In this case, the terminal-side device can further reset the number of times the first information is sent to 0. It should be noted that when the terminal-side device determines that the number of times the first information is sent is less than N and does not receive the second information from the network-side device, the terminal-side device may not actively perform BWP switching. Upon receiving the second information from the network-side device, the terminal-side device may switch, based on the second information, to the third BWP indicated by the second information. Step 4: The terminal-side device completes the BWP switchover, to recover from the constant uplink LBT failure. An example in which the terminal-side device switches to the second BWP is used below for the descriptions. The second BWP may include at least one of a resource for performing a random access procedure and an SR resource. For details, see the previous descriptions. Details are not described again here. When switching to the second BWP, the terminal-side device can recover from the constant uplink LBT failure by using a random access procedure or an SR procedure. In addition, the terminal-side device may send the first information to the network-side device in the random access procedure or in a resource scheduling request procedure. When the random access procedure is a two-step random access procedure, the terminal-side device may send the first piece of information by using a PUSCH resource determined based on a preamble and a PRACH occasion corresponding to the preamble in the two-step random access procedure. For details, see the previous descriptions. Details are not described again here. When the random access procedure is a four-step random access procedure, the terminal-side device may send the first piece of information by using an allocated uplink resource using a RAR message in the four-step random access procedure. For details, see the previous descriptions. Details are not described again here. When the terminal-side device performs the SR procedure, the terminal-side device can send the first information by using a requested uplink resource using SR. For details, see the previous descriptions. Details are not described again here. Implementation 3: Stage 1: A terminal-side device determines that a constant uplink LBT failure occurs at a first BWP of a first cell. Stage 2: The terminal-side device actively performs BWP switching on the first cell to switch to a second BWP of the first cell. The second BWP may include at least one of a resource for performing a random access procedure and an SR resource. For more details, see the previous descriptions. Details are not described again here. Stage 3: The terminal-side device may recover, at the second BWP, from the constant uplink LBT failure by using a two-step random access procedure, a four-step random access procedure, or an SR procedure. Step 4: The terminal-side device sends the first information about the uplink resource in the second cell when it determines that the start time of an uplink resource in a second cell is earlier than a sending time of payload data of an A msg in the two-step random access procedure, is earlier than a starting time of an uplink resource indicated by a RAR message in the four-step random access procedure, or is earlier than a sending time of an uplink resource requested by using an SR. Specifically, in a first scenario, payload data of msg A in the nAcnon / zznz / q / uyl two-step random access procedure is sent using a PUSCH resource that is determined based on a preamble and a PRACH occasion corresponding to the preamble in the two-step random access procedure. If the terminal-side device starts the two-step random access procedure in the second BWP by using the resource for performing the random access procedure in the second BWP, the terminal-side device sends first information by using the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of the PUSCH resource that is determined based on the preamble and the PRACH occasion corresponding to the preamble in the two-step random access procedure. In a second scenario, if the terminal-side device starts the four-step random access procedure in the second BWP by utilizing the resource for performing the random access procedure in the second BWP, the terminal-side device sends the first information by utilizing the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of the uplink resource allocated by utilizing the RAR message in the four-step random access procedure. In a third scenario, if the terminal-side device initiates the SR procedure at the second BWP by utilizing the SR resource at the second BWP, the terminal-side device sends the first information by utilizing the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of the uplink resource requested by utilizing the SR procedure. It should be noted that the terminal-side device may not send the first information about the uplink resource in the second cell when it determines that the start time of the uplink resource in the second cell is later than the sending time of the payload data of msg A in the two-step random access procedure, is later than the start time of the uplink resource indicated by the RAR message in the four-step random access procedure, or is later than the sending time of the requested uplink resource when using the SR. In addition, the terminal-side device can recover from the constant uplink LBT failure in the second BWP by using the random access procedure or the SR procedure. It is assumed that any of the above three scenarios are met. After the terminal-side device sends the first uplink resource information in the second cell, if the terminal-side device is performing the two-step random access procedure or the four-step random access procedure in the second BWP of the first cell, the terminal-side device may further perform any of the following operations: 1. Continue completing the two-step random access procedure or the four-step random access procedure started in the second BWP. 2. End the current two-step random access procedure or four-step random access procedure and switch back to the first BWP. In addition, when recovering from uplink LBT failure using random access procedure or SR procedure, the terminal-side device may send the first information by using random access procedure or SR procedure. For example, when the random access procedure is a two-step random access procedure, the terminal-side device may send the first information by using the PUSCH resource determined based on the preamble and the PRACH occasion corresponding to the preamble in the two-step random access procedure. For details, see the previous descriptions. Details are not described again here. When the random access procedure is the four-step random access procedure, the terminal-side device can send the first piece of information by using the allocated uplink resource using the RAR message in the four-step random access procedure. For details, see the previous descriptions. Details are not described again here. When the terminal-side device initiates the SR procedure, the terminal-side device can send the first information by using the requested uplink resource when using SR. For details, see the previous descriptions. Details are not described again here. An embodiment of this application further provides a method. Upon determining that a persistent uplink LBT failure occurs in a first BWP of a first cell, a terminal-side device may send the first information only through the first cell. For details, see a method shown in FIGURE 6. In the method shown in FIGURE 6, both the first cell and the second cell can serve the terminal-side device. The first cell is a primary cell or a primary secondary cell, and the second cell is a secondary cell. For more details, see FIGURE 6. The method includes the following steps. Step 601: The terminal-side device determines that the constant uplink LBT failure occurs at the first BWP of the first cell. Step 602: The terminal-side device switches to a second BWP of the first nAcnon / zznz / q / υιλι cell and sends the first information only in the second BWP of the first cell in the first cell and the second cell. The first information is used to indicate that the terminal-side device experiences constant uplink LBT failure in the first cell. The second cell is a cell in which a constant uplink LBT failure does not occur. It should be noted that if the second cell is a cell in which a constant uplink LBT failure does not occur, it may mean that when sending the first information, the terminal-side device does not experience the constant uplink LBT failure in the second cell, or it may mean that when determining an uplink resource used to send the first information, the terminal-side device does not experience the constant uplink LBT failure in the second cell. In the method shown in FIG. 6, the second BWP may include at least one resource for performing a random access procedure and an SR resource. The second BWP may include the resource for performing the random access procedure. The resource for performing the random access procedure may include at least one resource for performing a two-step random access procedure and a resource for performing a four-step random access procedure. The terminal-side device may perform the random access procedure in the second BWP by utilizing the resource for performing the random access procedure included in the second BWP, and send the first information by utilizing the random access procedure. For details, refer to the descriptions in the method shown in FIG. 4. Details are not described again herein. The second BWP may also include the SR resource. The terminal-side device may initiate an SR procedure by using the SR resource in the second BWP, to send the first information by using an uplink resource requested by using the SR procedure. A detailed procedure is not described again. In addition, before sending the first information in the second BWP of the first cell, the terminal-side device may determine whether there is an uplink resource available in the second cell. The uplink resource available in the second cell may be an uplink resource used for a new transmission in the second cell, and may include, but is not limited to, one or more of the following: a configured grant resource; and a resource scheduled by an encrypted PDCCH using a C-RNTI of the terminal-side device. For detailed content of the above resource, please refer to the descriptions in step 402. No details are described again here. nAcnon / zznz / q / υιλι When an uplink resource is available in the second cell, the terminal-side device does not yet send the first information when using the uplink resource in the second cell. In a possible implementation, upon determining that a start time of the available uplink resource in the second cell is earlier than a payload data sending time of an A msg in the two-step random access procedure, is earlier than a start time of an uplink resource indicated by a RAR message in the four-step random access procedure, or is earlier than a sending time of the requested uplink resource when using an SR, the terminal-side device does not yet use the uplink resource of the second cell. Alternatively, before sending the first information in the second BWP of the first cell, the terminal-side device may not determine whether an uplink resource is available in the second cell. In other words, regardless of whether an uplink resource is available in the second cell, the terminal-side device sends the first information in the second BWP of the first cell. In this embodiment of this application, when the terminal-side device determines that the constant uplink LBT failure occurs at a fourth BWP of a third cell, and the terminal-side device has not generated a MAC CE that includes indication information used to indicate that the constant uplink LBT failure occurs at the third cell, there are no clear solutions for how the terminal-side device currently performs processing if the terminal-side device determines to fail over to the BWP. Therefore, an embodiment of this application further provides a method for resolving the above problem. FIGURE 7 is a schematic flow diagram of a communication method according to one embodiment of this application. Step 701: A terminal-side device determines that a constant uplink LBT failure occurs at a fourth BWP of a third cell. For details on how the terminal-side device specifically determines that a persistent uplink LBT failure occurs, see the previous descriptions. Details are not described here. Step 702: Before generating the third information, the terminal-side device performs a first operation if it determines to switch to a fifth BWP of the third cell. The third information is used to indicate that the terminal-side device does not experience the constant uplink LBT failure in the third cell. For example, referring to FIGURE 7, as shown in FIGURE 8, the terminal-side device determines, at a first time, that the constant uplink LBT failure nAcnon / zznz / q / uylι occurs at the fourth BWP of the third cell. The terminal-side device determines to fail over to the fifth BWP of the third cell at a second time. Because the constant uplink LBT failure occurs in both the third cell and the fifth cell, the terminal-side device may send, via a fourth cell, a data packet carrying the third information. See FIGURE 8. The terminal-side device generates a first data packet at a third time. The first data packet is a newly transmitted data packet and may include the third information by using a Logical Channel Prioritization (LCP) procedure. It should be noted that, in FIG. 8, at a fourth time, if the terminal-side device experiences the constant uplink LBT failure in the fifth cell, the terminal-side device may alternatively report, to a network-side device, the third information carried in the first data packet. The third information is used to indicate that the terminal-side device experiences the constant uplink LBT failure in the fifth cell. For example, when the third information is a MAC CE, a specific operation may set a value of a bit in a cell identifier field corresponding to the fifth cell in the third information to a first value, e.g., set to 1. Optionally, the first data packet may be a MAC protocol data unit (PDU). The third piece of information may be the MAC CE. For a detailed structure of the MAC CE, see FIGURE 5. Optionally, a MAC CE used to indicate that a constant uplink LBT failure occurs may also be referred to as an LBT Failure MAC CE. Optionally, if the third cell is a secondary cell, upon receiving the DCI from the network-side device, the terminal-side device switches to the fifth BWP indicated by the DCI. The DCI is used to indicate that the terminal-side device switches to the fifth BWP. Optionally, if the third cell is a primary cell or a primary secondary cell, upon receiving the DCI from the network-side device, the terminal-side device may switch to the fifth BWP indicated by the DCI. Alternatively, the terminal-side device may actively trigger BWP switching to switch to the fifth BWP. It should be noted that, when the terminal-side device actively triggers BWP switching, a triggering condition for triggering BWP switching may be a triggering condition other than a persistent uplink LBT failure. For example, one possible triggering condition is sending different types of data to trigger BWP switching. Of course, this is just an example. The triggering condition may also include other cases, provided that BWP switching is not triggered by a persistent uplink LBT failure in the third cell. With reference to the above descriptions, in this embodiment of this application, the first operation may be any of the following operations: 1. Cancel a constant uplink LBT failure state of the third cell. Optionally, the terminal-side device may also send the first data packet that includes the third information. When the third information is the MAC CE shown in FIG. 5, the MAC CE may include a plurality of cell identifier fields. For example, FIG. 5 includes 31 cell identifier fields: C1 to C31. When a bit value corresponding to a cell identifier field is a first value, it indicates that the terminal-side device experiences the constant uplink LBT failure in a cell corresponding to the cell identifier field. When a bit value corresponding to a cell identifier field is a second value, it indicates that the terminal-side device does not experience the constant uplink LBT failure in a cell corresponding to the cell identifier field. The specific values ​​of the first value and the second value are not limited. For example, the first value is 1 and the second value is 0. For example, referring to the above examples, when the third information is MAC CE, a bit value in a cell identifier field corresponding to the third cell in the third information may be set to a second value, e.g., set to 0. 2. When performing packet assembly on the first data packet, the terminal-side device determines that if a persistent uplink LBT failure does not occur in a serving cell other than the third cell, the terminal-side device cancels the generation of the third information. In other words, the third information is not carried in the first data packet. The network-side device can accurately determine, according to the above operations, whether the constant uplink LBT failure occurs in the third cell, so as to avoid unnecessary BWP switching caused by mistakenly judging that the constant uplink LBT failure occurs in the third cell. 3. Maintain constant uplink LBT failure state of the third cell. Optionally, the terminal-side device no longer sends the third information, but may send a first data packet that includes the fourth information. nRcnon / zznz / q / υιλι The fourth information is used to indicate that the terminal-side device experiences the constant uplink LBT failure in the third cell. For example, referring to FIGURE 5, when the fourth information is MAC CE, a value of a bit in a cell identifier field corresponding to the third cell in the fourth information may be set to the first value, e.g., set to 1. 4. Maintain constant uplink LBT failure state of the third cell. Optionally, the terminal-side device may also send the first data packet that includes the fourth information. The fourth piece of information is used to indicate that the terminal-side device is experiencing a persistent uplink LBT failure in the third cell. The fourth piece of information can also be used to indicate the fourth BWP. For example, referring to the above possible implementation, the fourth information may further include at least one BWP identifier field, as shown in FIGURE 9. The BWP identifier field is used to indicate an identifier of a BWP at which the constant uplink LBT failure occurs. For example, if the first value is 1, the second value is 0. When a bit value corresponding to C1 is 1, a BWP 1 indicates an identifier of a BWP at which a constant uplink LBT failure occurs in a cell corresponding to C1. If the bit value corresponding to C1 is 0, and the bit value corresponding to C2 is 1, the BWP 1 indicates an identifier of a BWP at which the constant uplink LBT failure occurs in a cell corresponding to C2. Another case may be deduced by analogy. Details are not described further.BWP 1 is an identifier of a BWP in which the constant uplink LBT failure occurs in the first serving cell in which the constant uplink LBT failure occurs. Currently, a serving cell supports a maximum of four dedicated BWPs. Therefore, the BWP identifier field may include at least two bits. A specific number of bits included is not limited. A number of dedicated BWPs is expanded below, where the method is also applicable. Details are not described again here. Referring to FIGURE 9, the value of the bit in the cell identifier field corresponding to the third cell in the fourth information may be set to the first value, e.g., set to 1. In addition, the fourth information may additionally include the BWP identifier field. The BWP identifier field is used to carry an identifier of the fourth BWP. The network-side device may accurately determine, according to the above operations, whether the constant uplink LBT failure occurs in the nRcnon / zznz / q / υιλι third cell, and may further determine a BWP at which the constant uplink LBT failure occurs. The embodiments described in this specification may be stand-alone solutions or may be combined based on internal logic. All of these solutions are within the scope of protection of this application. It may be understood that in the above embodiments of the method, the methods and operations implemented by the terminal-side device may alternatively be implemented by a component (e.g., a chip or a circuit) that may be used in the terminal-side device. In the foregoing embodiments provided in this application, the methods provided in the embodiments of this application are described separately from a device interaction perspective. To implement functions in the method provided in the embodiments of this application, a terminal-side device may include a hardware structure and / or a software module, to implement the functions in the form of a hardware structure, a software module, or a hardware structure and a software module. Whether a function of the foregoing functions is realized using the hardware structure, the software module, or the combination of the hardware structure and the software module depends on the particular applications and the design constraints of the technical solutions. In embodiments of this application, the division into modules is an example and is only a logical division of function. Other forms of division may occur during actual implementation. Furthermore, the function modules in embodiments of this application may be integrated into a processor, or each module may exist only physically, or two or more modules may be integrated into a single module. The integrated module may be implemented in hardware or may be implemented as a software functional module. Similar to the above concept, as shown in FIG. 10, an embodiment of this application further provides an apparatus 1000 configured to implement a function of the terminal-side device or the network-side device in the above method. For example, the apparatus may be a software module or a system-on-chip. In this embodiment of this application, the system-on-chip may include a chip, or may include a chip and another discrete device. The apparatus 1000 may include a processing unit 1001 and a communication unit 1002. In this embodiment of this application, the communication unit may also be referred to as a transceiver unit and may include a sending unit and / or a receiving unit, which are respectively configured to perform the sending and receiving steps of the terminal-side device or the network device in the above nAcnon / zznz / q / υιλι embodiments of the method. The following describes in detail the communication apparatus provided in embodiments of this application with reference to FIG. 10 and FIG. 11. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments. Therefore, for content not described in detail, refer to the method embodiments above. For brevity, the details are not described further herein. For example, when the apparatus 1000 implements a function of the terminal-side device in the method shown in FIG. 4, the processing unit 1001 is configured to determine that the persistent uplink LBT listen-before-talk failure occurs in a first BWP bandwidth portion of a first cell, and the communication unit 1002 is configured to send the first information to the network-side device when utilizing an uplink resource in a second cell. The first information is used to indicate that the terminal-side device experiences the persistent uplink LBT failure in the first cell. The second cell is a cell in which the persistent uplink LBT failure does not occur. In a possible implementation, the processing unit 1001 is further configured to: starting a first timer, where the timing duration of the first timer is the first duration; and when the first timer expires, switching to a second BWP of the first cell if the communication unit does not receive, from the network-side device, second information in response to the first information, where the second BWP includes a resource for performing a random access procedure, and the second information is DCI downlink control information used to program the terminal-side device to perform the BWP switching; and performing the random access procedure in the second BWP by using the resource for performing the random access procedure. In a possible implementation, the communication unit is specifically configured to: sending, by the terminal-side device, the first information by utilizing the uplink resource in the second cell by determining that a number of times of sending the first information is less than N, where N is an integer greater than 1. In a possible implementation, the processing unit 1001 is further configured to: nAcnon / zznz / q / υιλι switching to a second BWP of the first cell by determining that the number of times of sending the first information is not less than N, where N is an integer greater than 1, and the second BWP includes a resource for performing a random access procedure; and performing the random access procedure in the second BWP by utilizing the resource for performing the random access procedure. In a possible implementation, when the random access procedure is a two-step random access procedure, the communication unit is configured to send the first information by using a physical uplink shared channel resource PUSCH that is determined based on a preamble and a physical random access channel occasion PRACH that corresponds to the preamble in the two-step random access procedure. Alternatively, when the random access procedure is a four-step random access procedure, the communication unit is configured to send the first information by using an allocated uplink resource by using a random access response message RAR in the four-step random access procedure. In one possible implementation, the communication unit 1002 is specifically configured to: switching to a second BWP of the first cell, where the second BWP includes a resource for performing a random access procedure; and starting a two-step random access procedure in the second BWP by using the resource for performing the random access procedure, and the terminal-side device sends first information by using the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of a PUSCH physical uplink shared channel resource that is determined based on a preamble and a PRACH physical random access channel occasion corresponding to the preamble in the two-step random access procedure;or start a four-step random access procedure in the second BWP when using the resource to perform the random access procedure, and the terminal-side device sends the first information when using the uplink resource in the second cell when a start time of the uplink resource in the second cell in the time domain is earlier than a start time of an uplink resource allocated using a random access response message RAR in the four-step random access procedure.; In one possible implementation, the first cell is a primary cell or a primary secondary cell, and the second cell is a secondary cell. nAcnon / zznz / q / υιλι For example, when the apparatus 1000 implements a terminal-side device function in the method shown in FIG. 6, the processing unit 1001 is configured to determine that the constant uplink LBT listen-before-talk failure occurs in a first BWP bandwidth portion of a first cell, where the first cell is a primary cell or a primary secondary cell, a second cell is a secondary cell, and the second cell is a cell in which a constant uplink LBT failure does not occur and includes an available uplink resource;and the communication unit 1002 is configured to: switch a second BWP of the first cell and send the first information on the second BWP of the first cell in the first cell and the second cell, where the first information is used to indicate that the terminal-side device experiences the constant uplink LBT failure in the first cell; In a first possible implementation, the second BWP includes a facility to perform a random access procedure. The 1002 communication unit is specifically configured for: performing the random access procedure in the second BWP by using the resource for performing the random access procedure; and when the random access procedure is a two-step random access procedure, the first information is sent by using a physical uplink shared channel resource PUSCH corresponding to a preamble in the two-step random access procedure; or when the random access procedure is a four-step random access procedure, the first information is sent by using an uplink resource allocated by using a random access response message RAR in the four-step random access procedure. For example, when the apparatus 1000 implements a terminal-side device function in the method shown in FIG. 7, the processing unit 1001 is configured to determine, by using the communication unit 1002, that a constant uplink LBT listen-before-talk failure occurs in a quarter of the BWP bandwidth of a third cell. The processing unit 1001 is configured to: before generating the third information, cancel a constant uplink LBT failure state of the third cell if the processing unit determines to switch to a fifth BWP of the third cell, where the third information is used to indicate that the terminal-side device does not experience the constant uplink LBT failure in the third cell. nAcnon / zznz / q / υιλι In one possible implementation, the processing unit 1001 is specifically configured to: receive DCI downlink control information from the network-side device, where the DCI is used to indicate that the terminal-side device switches to the fifth BWP. FIGURE 11 shows an apparatus 1100 according to one embodiment of this application. The apparatus shown in FIGURE 11 may be a hardware circuit implementation of the apparatus shown in FIGURE 10. The communication apparatus may be configured to perform a function of the terminal-side device in the above embodiments of the method. For ease of description, FIGURE 11 shows only the major components of the communication apparatus. The apparatus 1100 shown in FIGURE 11 includes at least one processor 1120. The apparatus 1100 may further include at least one memory 1130, configured to store program instructions and / or data. The memory 1130 is coupled to the processor 1120. The coupling in this embodiment of this application is an indirect coupling or communication connection between apparatuses, units, or modules for the exchange of information between the apparatuses, units, or modules, and may be electrical, mechanical, or other. The processor 1120 may cooperate with the memory 1130. The processor 1120 may execute the program instructions stored in the memory 1130. At least one of the at least one memory may be included in the processor. It should be noted that the processor in this embodiment of this application may be an integrated circuit chip and have signal processing capabilities. In one implementation process, the steps in the above embodiments of the method may be completed using a hardware integrated logic circuit in the processor or instructions in the form of software. The above processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. It can be understood that, in this embodiment of this application, the memory may be volatile or non-volatile memory, or may include both volatile and non-volatile memory. It should be noted that the memory in the system and method described in this specification includes, but is not limited to, these memories and any other appropriate memory. The apparatus 1100 may further include a communication interface 1110, configured to communicate with another device using a transmission medium, such that a device in the apparatus 1100 can communicate with another device. In this embodiment of this application, the communication interface may be a transceiver, a circuit, a bus, a module, or an other type of communication interface. In this embodiment of this application, when the communication interface is a transceiver, the transceiver may include a separate receiver and a separate transmitter, or may be a transceiver integrated with a transceiver function or an interface circuit. The apparatus 1100 may further include a communication line 1140. The communication interface 1110, the processor 1120, and the memory 1130 may be connected to each other via the communication line 1140. The communication line 1140 may be a peripheral component interconnect (PCI) bus, an extended industry standard architecture (EISA) bus, or the like. The communication line 1140 may be categorized into an address bus, a data bus, a control bus, and the like. For ease of representation, only one line is used in bold to represent the bus in FIG. 11, but this does not mean that there is only one bus or only one type of bus. For example, when the apparatus 1100 implements a terminal-side device function in the method shown in FIG. 4, the processor 1120 is configured to determine that the persistent uplink LBT listen-before-talk failure occurs in a first BWP bandwidth portion of a first cell, and the communication interface 1110 is configured to send the first information to a network-side device when utilizing an uplink resource in a second cell, where the first information is used to indicate that the terminal-side device experiences the persistent uplink LBT failure in the first cell, and the second cell is a cell in which a persistent uplink LBT failure does not occur. In a possible implementation, the processor 1120 is further configured to: start a first timer, where the timing duration of the first timer is the first duration; when the first timer expires, switching to a second BWP of the first cell if the communication unit does not receive, from the network-side device, second information in response to the first information, where the second BWP includes a resource for performing a random access procedure, and the second information is DCI downlink control information used to program the terminal-side device to perform the BWP switching; and performing the random access procedure in the second BWP by using the resource for performing the random access procedure. nAcnon / zznz / q / υιλι 1110, which occurs with a constant uplink LBT listen-before-talk failure in a quarter of the BWP bandwidth of a third cell. The processor 1120 is configured to: before generating the third information, cancel a constant uplink LBT failure state of the third cell if the processing unit determines to switch to a fifth BWP of the third cell, where the third information is used to indicate that the terminal-side device does not experience the constant uplink LBT failure in the third cell. In one possible implementation, the processor 1120 is specifically configured to: receive DCI downlink control information from a network-side device, where the DCI is used to indicate that the terminal-side device switches to the fifth BWP. One skilled in the art should understand that the embodiments of this application may be provided as a method, a system, or a computer program product. Thus, this application may utilize a form of a hardware-only embodiment, a software-only embodiment, or an embodiment with a combination of software and hardware. Moreover, this application may utilize a form of a computer program product that is implemented on one or more computer-usable storage media (including, but not limited to, disk memory, optical memory, and the like) that includes computer-usable program code. This application is described with reference to the flowcharts and / or block diagrams of the method, device (system), and computer program product according to this application. It should be understood that computer program instructions may be used to implement each process and / or block in the flowcharts and / or block diagrams, and a combination of a process and / or block in the flowcharts and / or block diagrams.These computer program instructions may be provided for a general-purpose computer, a dedicated computer, an embedded processor, or a processor of another programmable data processing device to generate a machine, such that the instructions executed by the computer or the processor of the other programmable data processing device generate an apparatus for implementing a specific function in one or more processes in the flowcharts and / or in one or more blocks in the block diagrams. These computer program instructions may alternatively be stored in a computer-readable memory that can instruct a computer or other programmable data processing device to operate in a specific manner, such that the instructions stored in the computer-readable memory generate an artifact that includes an instruction apparatus. The instruction apparatus implements a specific function in one or more processes in the flowcharts and / or in one or more blocks in the block diagrams. It is clear that a person skilled in the art can make various modifications and variations to this application without departing from the scope of this application. This application is intended to cover these modifications and variations of this application provided they are within the scope of protection defined by the following claims of this application and its equivalent technologies.

Claims

1. A communication method, characterized in that it comprises: determining, by means of a terminal-side device, that a constant uplink listen-before-talk (LBT) failure occurs in a bandwidth portion (BWP) of a cell; and canceling, by means of the terminal-side device, a constant uplink LBT failure state of the cell if the terminal-side device determines to switch to another BWP of the cell.

2. The method according to claim 1, characterized in that the determination to switch to the other cell BWP comprises: receiving, by means of the terminal-side device, downlink control information, DCI, from a network-side device, wherein the DCI indicates that the terminal-side device switches to the other BWP.

3. The method according to claim 1 or 2, characterized in that the method further comprises: generating, by means of the terminal-side device, the media access control element, CE, MAC, which indicates whether or not the terminal-side device experiences the constant uplink LBT failure in the cell.

4. The method according to claim 3, characterized in that the MAC CE indicates that the terminal-side device does not experience constant uplink LBT failure in the cell after the terminal cancels the constant uplink LBT failure state of the cell.

5. The method according to claim 3, characterized in that the MAC CE indicates that the terminal-side device experiences the constant uplink LBT failure in the cell before the terminal cancels the constant uplink LBT failure state of the cell.

6. The method in accordance with any of claims 3 to 5, characterized in that the MAC CE includes a cell identifier field, a bit value of which indicates whether or not the terminal-side device experiences constant uplink LBT failure in the cell.

7. The method in accordance with any of claims 1 to 6, characterized in that the cell is a primary cell, a primary secondary cell or a secondary cell.

8. The method according to any one of claims 1 to 7, characterized in that the determination, by means of the terminal-side device, that a constant uplink LBT fault occurs in the cell BWP comprises: performing, by means of the terminal-side device, an uplink LBT in the cell BWP; if the terminal-side device determines that each time an uplink LBT fault occurs in the BWP, the following operations are performed by means of the terminal-side device: incrementing a count value of an LBT fault counter by 1, where an initial value of the counter is 0; starting or resetting a timer; determining that a constant uplink LBT fault occurs in the cell BWP when the timer does not expire and the count value of the LBT fault counter reaches a threshold.

9. The method according to claim 8, characterized in that the method further comprises: resetting, by means of the terminal-side device when the timer expires, the LBT fault counter count value to 0.

10. A communication apparatus, characterized in that it is configured to perform the method according to any of claims 1 to 9.

11. A computer-readable storage medium, characterized in that it comprises computer-readable instructions, wherein, when a communication apparatus reads and executes the computer-readable instructions, the communication apparatus is enabled to perform the method according to any one of claims 1 to 9.

12. A computer program product, characterized in that it comprises computer-readable instructions, wherein, when a communication apparatus reads and executes the computer-readable instructions, the communication apparatus is enabled to perform the method according to any one of claims 1 to 9.

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