A first node transmits a first signal; receives a second signal; and transmits a third signal on a target time-frequency resource block; the second signal is used to indicate a first time-frequency resource block, the first time-frequency resource block is used to determine a target time-frequency resource set, and the first time-frequency resource block is one of the multiple time-frequency resource blocks comprised in the target time-frequency resource set; the target time-frequency resource block is one of the multiple time-frequency resource blocks comprised in the target time-frequency resource set, and whether the third signal carries a first-type information block is used to determine the target time-frequency resource block out of the target time-frequency resource set; the first-type information block comprises control-plane information. The present application transmits a Message 3 through additional time-frequency resources to reduce the conflict of random access to mainstream services.