A method includes: determining a maximum orthogonal frequency division multiplexing OFDM symbol quantity of a frequency band used for downlink transmission, where the maximum OFDM symbol quantity of the frequency band is a maximum value of maximum OFDM symbol quantities of all subbands of the frequency band; determining, according to a value relationship between a maximum OFDM symbol quantity of a subband to which user equipment belongs and the maximum OFDM symbol quantity of the frequency band, additional long training field instruction information used to instruct whether to send an additional long training field to the user equipment; and sending an indication message to the user equipment, where the indication message includes the additional long training field instruction information.