A method performed by a radio link control, RLC, entity (3d-10, 3d-35) in a receiving device in a wireless communication system, the method comprising: identifying (3j-05) if a timer for detecting loss of RLC protocol data units, PDUs, is not running, wherein an RLC PDU includes a RLC header and RLC data, the RLC data including a complete RLC service data unit, SDU, or an RLC SDU segment, and wherein the RLC header of the RLC PDU includes segmentation info, SI, field, the SI field indicating whether the RLC PDU contains the complete RLC SDU or the RLC SDU segment, the RLC SDU segment including a first segment, a middle segment, or a last segment; in case that the timer is not running (3j-20), identifying that a value of a state variable, RX_NEXT_Highest_ Rcvd, is equal to a value of a state variable, RX _NEXT, plus 1 and there is at least one missing segment of an RLC SDU before a last segment of all received segments of the RLC SDU, the RLC SDU being associated with a sequence number, SN, which is same as the value of the RX_NEXT; based on the identification that the value of the RX_NEXT_Highest_Rcvd is equal to the value of the RX_NEXT plus 1 and there is the at least one missing segment of the RLC SDU before the last segment of the all received segments of the RLC SDU, starting the timer and setting a value of a state variable, RX_NEXT_Status_Trigger, to the value of the RX_NEXT_Highest_ Rcvd; and in case that the timer is expired, updating a value of a state variable, RX Highest_Status, to a value of an SN of a first RLC SDU for which not all bytes have been received, wherein the value of the SN of the first RLC SDU is greater than or equal to the value of the RX_NEXT_Status_Trigger, and wherein the RX_NEXT_Highest_Rcvd holds a value of an SN following an SN of an RLC SDU with a highest SN among received RLC SDUs, wherein the RX_NEXT holds a value of an SN following a last in-sequence completely received RLC SDU, wherein the RX_NEXT_Status_Trigger holds a value of an SN following an SN of the RLC SDU which started the timer, and wherein the RX_Highest_Status holds a highest possible value of an SN indicated by ACK_SN when a STATUS PDU needs to be constructed, the ACK_SN indicating an SN of a next RLC SDU which is not received and not reported as missing in the STATUS PDU, and the STATUS PDU being used to inform whether the RLC PDUs are received successfully. identifying (3j-05) if a timer for detecting loss of RLC protocol data units, PDUs, is not running, wherein an RLC PDU includes a RLC header and RLC data, the RLC data including a complete RLC service data unit, SDU, or an RLC SDU segment, and wherein the RLC header of the RLC PDU includes segmentation info, SI, field, the SI field indicating whether the RLC PDU contains the complete RLC SDU or the RLC SDU segment, the RLC SDU segment including a first segment, a middle segment, or a last segment; in case that the timer is not running (3j-20), identifying that a value of a state variable, RX_NEXT_Highest_ Rcvd, is equal to a value of a state variable, RX _NEXT, plus 1 and there is at least one missing segment of an RLC SDU before a last segment of all received segments of the RLC SDU, the RLC SDU being associated with a sequence number, SN, which is same as the value of the RX_NEXT; based on the identification that the value of the RX_NEXT_Highest_Rcvd is equal to the value of the RX_NEXT plus 1 and there is the at least one missing segment of the RLC SDU before the last segment of the all received segments of the RLC SDU, starting the timer and setting a value of a state variable, RX_NEXT_Status_Trigger, to the value of the RX_NEXT_Highest_ Rcvd; and in case that the timer is expired, updating a value of a state variable, RX Highest_Status, to a value of an SN of a first RLC SDU for which not all bytes have been received, wherein the value of the SN of the first RLC SDU is greater than or equal to the value of the RX_NEXT_Status_Trigger, and wherein the RX_NEXT_Highest_Rcvd holds a value of an SN following an SN of an RLC SDU with a highest SN among received RLC SDUs, wherein the RX_NEXT holds a value of an SN following a last in-sequence completely received RLC SDU, wherein the RX_NEXT_Status_Trigger holds a value of an SN following an SN of the RLC SDU which started the timer, and wherein the RX_Highest_Status holds a highest possible value of an SN indicated by ACK_SN when a STATUS PDU needs to be constructed, the ACK_SN indicating an SN of a next RLC SDU which is not received and not reported as missing in the STATUS PDU, and the STATUS PDU being used to inform whether the RLC PDUs are received successfully.