A ML entity performs a backoff procedure of the primary link based on the backoff counter of the primary link; and when a count value of the backoff counter is 0, the ML entity sends a first PPDU on each first link in K first links, where the K first links include the primary link and K−1 first nonprimary links, and the first nonprimary link is in an idle state in a first inter-frame space before a time point at which the count value of the backoff counter decreases to 0.