For example, the network device may indicate that a corresponding time-domain position is downlink transmission via DCI format 1, and indicate that a corresponding time-domain position is uplink transmission via DCI format 0. When a control signaling format detected by a UE is DCI format 1, it may learn that a corresponding time-domain position is downlink transmission, and the UE needs to select an RACH resource of another time-domain position in the set of RACH resources.

In another example of the implementation, whether the RACH resources are available may be indicated by indicating whether preambles and data are permitted to be transmitted in the random access request. With this indication information, the network device may implicitly inform the UE of whether an RACH resource at a time-domain position supporting transmission of preambles and data is available. For example, when the UE detects that the control signaling does not permit to transmit preambles and data in the random access request, it may learn that RACH resources used for transmitting preambles and data are unavailable, and RACH resources transmitting preambles only need to be reselected.

In a further example of the implementation, whether the RACH resources are available may be explicitly indicated via RACH resource indication information, that is, the network device directly indicates whether the RACH resources are available via the RACH resource indication information.