at least one processor; and

one or more memories coupled to the at least one processor and storing programming instructions for execution by the at least one processor to:

receive an uplink signal from a terminal device in response to determining that a first variation meets a timing advance (TA) update condition, wherein the first variation indicates a strength change value of a downlink signal received by the terminal device;

generate first information based on the uplink signal, wherein in response to determining that TA information can be generated, the first information comprises the TA information, and the TA information indicates the terminal device to adjust an uplink transmission time;

send the first information to the terminal device; and

receive a random access request that carries a first preamble from the terminal device, wherein the first preamble is a preamble configured by the network device for the terminal device, and wherein the random access request is sent by the terminal device in response to determining that the first variation does not meet the TA update condition and that a timer configured by the terminal device expires.