A method performed by a terminal for hybrid automatic repeat request, HARQ, in a wireless communication system, the method comprising: receiving a downlink resource assignment on a downlink control channel; identifying whether the received downlink resource assignment is for a user equipment's, UE's, cell-radio network temporary identifier, C-RNTI; determining, in case that the received downlink resource assignment is for the UE's C-RNTI, whether a previous downlink resource assignment, which was received before the received downlink resource assignment, in a HARQ process corresponding to the received downlink resource assignment was configured for semi-persistent scheduling, SPS; determining, in case of determining that the previous downlink resource assignment was configured for the SPS, whether a HARQ entity of the same HARQ process was indicated to receive data at an SPS occasion based on resources allocated according to the previous downlink resource assignment; and in case of determining that the HARQ entity of the same HARQ process was indicated to receive data at the SPS occasion based on resources allocated according to the previous downlink resource assignment: considering that a new data indicator, NDI, of the received downlink resource assignment is toggled regardless of a value of the NDI, and attempting to decode received data, characterized in that in case that the SPS occasion is overlapped with a measurement gap, an SPS resource corresponding to the SPS occasion is not used and a HARQ buffer for the HARQ entity of the same HARQ process is not flushed. receiving a downlink resource assignment on a downlink control channel; identifying whether the received downlink resource assignment is for a user equipment's, UE's, cell-radio network temporary identifier, C-RNTI; determining, in case that the received downlink resource assignment is for the UE's C-RNTI, whether a previous downlink resource assignment, which was received before the received downlink resource assignment, in a HARQ process corresponding to the received downlink resource assignment was configured for semi-persistent scheduling, SPS; determining, in case of determining that the previous downlink resource assignment was configured for the SPS, whether a HARQ entity of the same HARQ process was indicated to receive data at an SPS occasion based on resources allocated according to the previous downlink resource assignment; and in case of determining that the HARQ entity of the same HARQ process was indicated to receive data at the SPS occasion based on resources allocated according to the previous downlink resource assignment: considering that a new data indicator, NDI, of the received downlink resource assignment is toggled regardless of a value of the NDI, and attempting to decode received data, characterized in that in case that the SPS occasion is overlapped with a measurement gap, an SPS resource corresponding to the SPS occasion is not used and a HARQ buffer for the HARQ entity of the same HARQ process is not flushed. considering that a new data indicator, NDI, of the received downlink resource assignment is toggled regardless of a value of the NDI, and attempting to decode received data, characterized in that in case that the SPS occasion is overlapped with a measurement gap, an SPS resource corresponding to the SPS occasion is not used and a HARQ buffer for the HARQ entity of the same HARQ process is not flushed.