Techniques for performing a handover in a network with a relay node (RN) are disclosed. The RN is a node deployed between an eNodeB (eNB) and a wireless transmit/receive unit (WTRU). The RN receives data from one of the eNB and the WTRU and forwards it to the other. The RN receives a packet data convergence protocol (PDCP) protocol data unit (PDU) from a serving donor evolved Node-B (DeNB) and transmits it to the WTRU. The RN makes a handover decision based on the measurement report received from the WTRU. After making a handover decision, the RN sends a handover request or a control message to the serving DeNB including a first unsuccessfully transmitted PDCP sequence number (SN). The serving DeNB then discards a PDCP PDU with an SN older than the first unsuccessfully transmitted PDCP SN.