A method for transmitting uplink, UL, data by a user equipment, UE, in a wireless communication system supporting an unlicensed band, the method comprising: receiving scheduling information for UL data transmission on an licensed assisted access, LAA, secondary cell, SCell, in the unlicensed band, wherein the UL data transmission comprises the UL data, wherein the scheduling information comprises: (i) first offset information received on a first time resource, (ii) second offset information received on a second time resource and (iii) starting position information of the UL data transmission, wherein the second offset information is cell-commonly or group-commonly received through a physical downlink control channel, PDCCH; identifying a maximum timing advance, TA, value for the UE based on the first offset information, the second offset information and the starting position information; and based on the maximum TA value being less than a TA value configured to the UE, dropping the UL data transmission in a third time resource comprising a starting time position of the UL data transmission related to the starting position information, wherein the third time resource is identified based on the first offset information and the second offset information, wherein each of the first time resource, the second time resource and the third time resource is configured as 14 orthogonal frequency division multiplexing, OFDM, symbols, wherein the third time resource is a time resource after a time duration from the second time resource, wherein the time duration is related with the sum of a value related with the first offset information and a value related with the second offset information, and wherein the starting position information informs, as the starting time position in the third time resource, one of: symbol#0 boundary, symbol#0 boundary + 25 μs, symbol#0 boundary + 25 μs + TA value configured to the UE, and symbol#1 boundary. receiving scheduling information for UL data transmission on an licensed assisted access, LAA, secondary cell, SCell, in the unlicensed band, wherein the UL data transmission comprises the UL data, wherein the scheduling information comprises: (i) first offset information received on a first time resource, (ii) second offset information received on a second time resource and (iii) starting position information of the UL data transmission, wherein the second offset information is cell-commonly or group-commonly received through a physical downlink control channel, PDCCH; identifying a maximum timing advance, TA, value for the UE based on the first offset information, the second offset information and the starting position information; and based on the maximum TA value being less than a TA value configured to the UE, dropping the UL data transmission in a third time resource comprising a starting time position of the UL data transmission related to the starting position information, wherein the third time resource is identified based on the first offset information and the second offset information, wherein each of the first time resource, the second time resource and the third time resource is configured as 14 orthogonal frequency division multiplexing, OFDM, symbols, wherein the third time resource is a time resource after a time duration from the second time resource, wherein the time duration is related with the sum of a value related with the first offset information and a value related with the second offset information, and wherein the starting position information informs, as the starting time position in the third time resource, one of: symbol#0 boundary, symbol#0 boundary + 25 μs, symbol#0 boundary + 25 μs + TA value configured to the UE, and symbol#1 boundary. symbol#0 boundary, symbol#0 boundary + 25 μs, symbol#0 boundary + 25 μs + TA value configured to the UE, and symbol#1 boundary.