TECHNICAL FIELD

This application relates to the communications field, and more specifically, to a method and an apparatus for monitoring a downlink control channel, a computer readable storage medium, and a terminal device.

BACKGROUND

A downlink control channel such as a physical downlink control channel (PDCCH) is used as a core of system resource allocation and control information scheduling. A receiving speed of the downlink control channel has important impact on a reaction speed of a communications system.

The downlink control channel carries downlink control information (DCI) of one or more terminal devices. For example, a terminal device receives downlink scheduling allocation information required for demodulation, decoding, and the like after receiving a physical downlink shared channel (PDSCH). The downlink scheduling allocation information is used to notify the terminal device of scheduling grant information, such as a resource and a transmission format, that needs to be used during physical uplink shared channel (PUSCH) transmission, acknowledgment information of shared channel transmission, and control information such as transmit power control signaling used for power control of an uplink physical channel.

There are a plurality of formats for DCI. DCI in different formats carries different information and has different functions. For example, a DCI format 0 is corresponding to PUSCH scheduling information, DCI formats 1, 1A, 1B, 1C, and 1D are corresponding to PDSCH scheduling information, DCI formats 1 and 2A are corresponding to some configuration information for a multi-antenna scenario, and a DCI format 3/3A is corresponding to some configuration information for uplink power control.

Usually, a terminal device does not know a format of DCI transmitted on a current downlink control channel, and does not know a location of information required by the terminal device, either. However, the terminal device knows information currently required by the terminal device.

For example, in an idle state, the terminal device expects paging information and system information. After initiating a random access preamble, the terminal device expects random access response information. When uplink data is to be sent, the terminal device expects uplink grant information and the like.

The terminal device may first decode different expected information, descramble a cyclic redundancy check (CRC) code by using a corresponding radio network temporary identifier (RNTI), and perform CRC check. If the check succeeds, the terminal device knows that the information is required by the terminal device, and also knows a corresponding DCI format, so that DCI content can further be decoded. This process may be referred to as a blind detection process of a downlink control channel.

A control channel element (CCE) is proposed in a communications system, to reduce a blind detection process of a downlink control channel. One CCE may include a plurality of resource element groups (REG).

One downlink control channel may include n consecutive CCEs, and the n CCEs may be referred to as a CCE set. The terminal device may monitor the downlink control channel on the CCEs.

A network device may configure one or more control resource sets (CORESET) for the terminal device. Each CORESET is associated with CCE-to-REG mapping. The terminal device may attempt to decode each downlink control channel on a CCE in a CORESET based on an expected DCI format. A set including candidate locations of a downlink control channel that needs to be monitored by the terminal device is defined as a search space of the downlink control channel. The search space may be understood as a CCE set on which monitoring needs to be performed and that is preset by the terminal device.

Assuming that the terminal device makes a blind detection attempt based on a given CCE aggregation level, a search space is a set including candidate locations of a downlink control channel in a CCE set defined based on the given aggregation level.

Usually, the network device configures a CORESET, an aggregation level, a quantity of candidate locations of a downlink control channel that are corresponding to each aggregation level, and a monitoring moment of a search space for the terminal device. In this way, the terminal device may monitor downlink control information based on these pieces of information. The terminal device may obtain, based on these pieces of information, a quantity of times the terminal device needs to attempt to decode the downlink control channel during monitoring.

However, a quantity of times the terminal device is capable of decoding the downlink control channel in a time period is limited. For example, the quantity of times is limited by a capability of the terminal device. Therefore, a method for monitoring a downlink control channel needs to be proposed to facilitate normal communication between a terminal device and a network device when a quantity of times the terminal device needs to attempt to decode a downlink control channel in a time period is greater than a maximum quantity of times the terminal is capable of decoding the downlink control channel in the corresponding time.

SUMMARY

This application provides a method for monitoring a downlink control channel and a related apparatus, to help ensure that a terminal device can detect a useful downlink control channel, thereby helping ensure normal communication between the terminal device and a network device.

According to a first aspect, this application provides a method for monitoring a downlink control channel. The monitoring method includes determining, by a terminal device, priority information, where the priority information includes at least one of the following: a control resource set priority, a search space priority, a downlink control information priority, or a downlink control information size priority, monitoring, by the terminal device, a downlink control channel based on the priority information, and obtaining, by the terminal device, downlink control information from the downlink control channel.

In the monitoring method, the terminal device may monitor the downlink control channel based on at least one of the following priorities: the control resource set priority, the search space priority, the downlink control information priority, or the downlink control information size priority, and obtain the downlink control information from the downlink control channel. This helps ensure that the terminal device preferentially monitors a useful downlink control channel, thereby helping ensure normal communication between the terminal device and a network device.

In a possible design, the control resource set priority includes a priority of a control resource set carrying first downlink control information is higher than that of a control resource set carrying second downlink control information, where the first downlink control information includes at least one of the following downlink control information: scheduling information of system information, scheduling information of a random access response message, scheduling information of uplink data, scheduling information of downlink data, a transmit power control command of a physical uplink shared channel, a transmit power control command of a physical uplink control channel, a transmit power control command of a sounding reference signal, scheduling information of a semi-persistent scheduling service, or scheduling information of a grant-free service, and the second downlink control information includes at least one of the following downlink control information: slot format indication information, discontinuous transmission indication information, or buffer flushing indication information.

In another possible design, the control resource set priority includes a priority of a control resource set carrying first downlink control information is higher than that of a control resource set carrying second downlink control information, where the first downlink control information is slot format indication information, and the second downlink control information includes at least one of the following downlink control information: discontinuous transmission indication information or buffer flushing indication information.

In another possible design, the control resource set priority includes a control resource set carrying first downlink control information has a highest priority, where the first downlink control information is scheduling information of a beam-failure-recovery-request response message.

In the first, second, or third implementation, a specific priority of a control resource set is provided, so that the terminal device may detect the downlink control channel based on the priority of the control resource set.

In another possible design, the search space priority includes a priority of a search space in which first downlink control information is located is higher than that of a search space in which second downlink control information is located, where the first downlink control information includes at least one of the following downlink control information: scheduling information of system information, scheduling information of a random access response message, scheduling information of uplink data, scheduling information of downlink data, a transmit power control command of a physical uplink shared channel, a transmit power control command of a physical uplink control channel, a transmit power control command of a sounding reference signal, scheduling information of a semi-persistent scheduling service, or scheduling information of a grant-free service, and the second downlink control information includes at least one of the following downlink control information: slot format indication information, discontinuous transmission indication information, or buffer flushing indication information.

In another possible design, the search space priority includes a priority of a search space in which first downlink control information is located is higher than that of a search space in which second downlink control information is located, where the first downlink control information is slot format indication information, and the second downlink control information includes at least one of the following downlink control information: discontinuous transmission indication information or buffer flushing indication information.

In another possible design, the search space priority includes a search space in which first downlink control information is located has a highest priority, where the first downlink control information is scheduling information of a beam-failure-recovery-request response message.

In this implementation, a specific priority of the search space is provided, so that the terminal device may detect the downlink control channel based on the priority of the search space.

In another possible design, the downlink control information priority includes a priority of first downlink control information is higher than that of second downlink control information, where the first downlink control information includes at least one of the following downlink control information: scheduling information of system information, scheduling information of a random access response message, scheduling information of uplink data, scheduling information of downlink data, a transmit power control command of a physical uplink shared channel, a transmit power control command of a physical uplink control channel, a transmit power control command of a sounding reference signal, scheduling information of a semi-persistent scheduling service, or scheduling information of a grant-free service, and the second downlink control information includes at least one of the following downlink control information: slot format indication information, discontinuous transmission indication information, or buffer flushing indication information.

In another possible design, the downlink control information priority includes a priority of first downlink control information is higher than that of second downlink control information, where the first downlink control information is slot format indication information, and the second downlink control information includes at least one of the following downlink control information: discontinuous transmission indication information or buffer flushing indication information.

In another possible design, the downlink control information priority includes first downlink control information has a highest priority, where the first downlink control information is scheduling information of a beam-failure-recovery-request response message.

In another possible design, the downlink control information size priority includes a priority of a downlink control information size of first downlink control information is higher than that of a downlink control information size of second downlink control information, where the first downlink control information includes at least one of the following downlink control information: scheduling information of system information, scheduling information of a random access response message, scheduling information of uplink data, scheduling information of downlink data, a transmit power control command of a physical uplink shared channel, a transmit power control command of a physical uplink control channel, a transmit power control command of a sounding reference signal, scheduling information of a semi-persistent scheduling service, or scheduling information of a grant-free service, and the second downlink control information includes at least one of the following downlink control information: slot format indication information, discontinuous transmission indication information, or buffer flushing indication information.

In another possible design, the downlink control information size priority includes a priority of a downlink control information size of first downlink control information is higher than that of a downlink control information size of second downlink control information, where the first downlink control information is slot format indication information, and the second downlink control information includes at least one of the following downlink control information: discontinuous transmission indication information or buffer flushing indication information.

In another possible design, the downlink control information size priority includes a downlink control information size of first downlink control information has a highest priority, where the first downlink control information is scheduling information of a beam-failure-recovery-request response message.

In another possible design, before the monitoring, by the terminal device, a downlink control channel based on the priority information, the monitoring method further includes determining, by the terminal device, that a quantity of times the terminal device needs to attempt to decode the downlink control channel in a first time period is greater than a quantity of times the terminal device is capable of decoding the downlink control channel in the first time period.

In other words, the terminal device monitors the downlink control channel based on the priority information only when the terminal device determines that the quantity of times the terminal device needs to attempt to decode the downlink control channel in the first time period is greater than the quantity of times the terminal device is capable of decoding the downlink control channel in the first time period. This can ensure that a downlink control channel with a higher priority can be preferentially detected when the quantity of times the terminal device needs to attempt to decode the downlink control channel in the first time period is greater than the quantity of times the terminal device is capable of decoding the downlink control channel in the first time period, thereby ensuring normal communication between a network device and the terminal device.

In another possible design, before the monitoring, by the terminal device, a downlink control channel based on the priority, the monitoring method further includes determining, by the terminal device, a first decoding quantity based on a first parameter and the quantity of times the terminal device needs to attempt to decode the downlink control channel in the first time period, where the first parameter is configured by a network device or is predefined, and determining, by the terminal device, that the first decoding quantity is greater than a quantity of times the terminal device is capable of decoding the downlink control channel in the first time period.

In other words, the terminal device determines the first decoding quantity based on the first parameter and the quantity of times the terminal device needs to attempt to decode the downlink control channel in the first time period, and then compares the first decoding quantity with the quantity of times the terminal device is capable of decoding the downlink control channel in the first time period, so that the terminal device has a greater opportunity to detect a downlink control channel with a lower priority.

In addition, the downlink control channel is monitored based on the priority information only when the first decoding quantity is greater than the quantity of times the terminal device is capable of decoding the downlink control channel in the first time period. This can ensure that a downlink control channel with a higher priority can be preferentially detected when the quantity of times the terminal device needs to attempt to decode the downlink control channel in the first time period is greater than the quantity of times the terminal device is capable of decoding the downlink control channel in the first time period, thereby ensuring normal communication between the network device and the terminal device.

In another possible design, the terminal device monitors a downlink control channel carrying a carrier indicator field, the terminal device monitors a downlink control channel carrying a bandwidth part BWP indicator field, or the terminal device monitors downlink control channels sent by a plurality of transmission reception points.

According to a second aspect, an embodiment of this application provides a downlink control channel monitoring apparatus, where the apparatus has a function of implementing behavior of the terminal device in the foregoing method designs. The function may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or the software includes one or more modules corresponding to the foregoing function, for example, a processor and a memory. The memory stores a related instruction, and the processor executes the instruction stored in the memory, to complete the processing steps in the foregoing method performed by the terminal device.

In a possible design, the monitoring apparatus includes a receiver, a processor, and a transmitter, and the receiver and the transmitter are configured to support communication between the terminal device and a network device. The processor is configured to determine priority information based on indication information received by the receiver, monitor downlink control information based on the priority information, and obtain the downlink control information from the downlink control channel. The network device may further include a memory. The memory is coupled to the processor, and the memory stores a program instruction and data that are necessary for the network device.

According to a third aspect, this application provides a computer readable storage medium. The computer readable storage medium stores program code executed by a terminal device. The program code includes an instruction that is used to perform the monitoring method in any one of the first aspect or the possible implementations of the first aspect.

According to a fourth aspect, this application provides a computer program product including an instruction. When the computer program product is run on a terminal device, the terminal device is enabled to perform the monitoring method in any one of the first aspect or the possible implementations of the first aspect.

According to a fifth aspect, this application provides a system chip. The system chip includes an input/output interface, at least one processor, at least one memory, and a bus. The at least one memory is configured to store an instruction, and the at least one processor is configured to invoke the instruction in the at least one memory, to perform the operations of the monitoring method in any one of the first aspect or the possible implementations of the first aspect.

According to a sixth aspect, this application provides a terminal device. The terminal device includes the monitoring device in the second aspect.

