Patent ID: 8514814

Claim:
A method for reporting Service Data Unit (SDU) reception status in a Packet Data Convergence Protocol (PDCP) layer of a mobile communications system, the method comprising: determining, at a receiving side of the PDCP layer, the reception status for each of a number of sequentially transmitted PDCP SDUs; generating, at the receiving side of the PDCP layer, a reception status report for the PDCP SDUs indicating whether or not each of the sequentially transmitted SDUs has been successfully received at the receiving side of the PDCP layer, wherein the reception status report is transmitted in the form of a bitmap and sequence number (SN) information, wherein each bit in the bitmap indicates whether or not a corresponding one of the PDCP SDUs has successfully been received and wherein the SN information, at least in part, is useable for identifying each SDU corresponding to a bit in the bitmap; and transmitting the reception status report to a transmitting side of the PDCP layer, wherein the method is performed during a handover operation.