A method performed by a wireless transmit receive unit, WTRU, for two-stage reordering of received protocol data units, PDUs, the method comprising: receiving PDUs from a plurality of Node-Bs, wherein each of the PDUs has a transmission sequence number, TSN, assigned independently at each of the plurality of Node-Bs; reordering the received PDUs from each of the plurality of Node-Bs, using the respective TSN of each received PDU, in different reordering queues of a medium access control, MAC, layer; delivering the PDUs from a plurality of reordering queues to one logical channel of a radio link control, RLC, layer; reordering the received PDUs in a reordering buffer of the RLC layer based on a sequence number, SN; on a condition that there is at least one missing RLC PDU detected based on a SN of at least one of the received RLC PDUs, starting a timer for each of the at least one missing RLC PDU and storing the at least one of the received RLC PDUs in the reordering buffer at a place indicated by the SN of each of the at least one of the received RLC PDUs; on a condition that the timer associated with a missing RLC PDU is running, delaying transmission of a status report indicating the SN of the missing RLC PDU; on a condition that the timer associated with a missing PDU has expired, transmitting the status report indicating the SN of the missing RLC PDU, and on a condition that a RLC PDU is received with a SN higher than an upper end of a receiving window: moving the receiving window to the SN higher than the upper end of the receiving window; stopping instances of timers associated with missing RLC PDUs whose SNs are below the receiving window; reassembling a RLC SDU with PDUs stored in the reordering buffer and transmitting a corresponding SDU to an upper entity; and removing the at least one of the received RLC PDUs with SNs below the receiving window from the reordering buffer. receiving PDUs from a plurality of Node-Bs, wherein each of the PDUs has a transmission sequence number, TSN, assigned independently at each of the plurality of Node-Bs; reordering the received PDUs from each of the plurality of Node-Bs, using the respective TSN of each received PDU, in different reordering queues of a medium access control, MAC, layer; delivering the PDUs from a plurality of reordering queues to one logical channel of a radio link control, RLC, layer; reordering the received PDUs in a reordering buffer of the RLC layer based on a sequence number, SN; on a condition that there is at least one missing RLC PDU detected based on a SN of at least one of the received RLC PDUs, starting a timer for each of the at least one missing RLC PDU and storing the at least one of the received RLC PDUs in the reordering buffer at a place indicated by the SN of each of the at least one of the received RLC PDUs; on a condition that the timer associated with a missing RLC PDU is running, delaying transmission of a status report indicating the SN of the missing RLC PDU; on a condition that the timer associated with a missing PDU has expired, transmitting the status report indicating the SN of the missing RLC PDU, and on a condition that a RLC PDU is received with a SN higher than an upper end of a receiving window: moving the receiving window to the SN higher than the upper end of the receiving window; stopping instances of timers associated with missing RLC PDUs whose SNs are below the receiving window; reassembling a RLC SDU with PDUs stored in the reordering buffer and transmitting a corresponding SDU to an upper entity; and removing the at least one of the received RLC PDUs with SNs below the receiving window from the reordering buffer. moving the receiving window to the SN higher than the upper end of the receiving window; stopping instances of timers associated with missing RLC PDUs whose SNs are below the receiving window; reassembling a RLC SDU with PDUs stored in the reordering buffer and transmitting a corresponding SDU to an upper entity; and removing the at least one of the received RLC PDUs with SNs below the receiving window from the reordering buffer.