A downlink transmission timing determination method performed by an integrated access and backhaul (IAB) node comprises: receiving a synchronization offset from a parent node; receiving a parameter related to a timing advance (TA) between an uplink transmission timing and a downlink reception timing; and on the basis of the synchronization offset and the parameter, determining a downlink transmission timing, wherein in comparison with the downlink reception timing, the downlink transmission timing has a time difference corresponding to a value calculated on the basis of the synchronization offset and the parameter.