Patent ID: 7760634

Claim:
A transmitting device having an acknowledged mode (AM) radio link control (RLC) entity in a mobile communication system, comprising: a segmentation and concatenation module that at least segments or concatenates service data units (SDUs) received from an upper layer; a header adding module that adds RLC headers to the at least segmented or concatenated SDUs for forming protocol data units (PDUs); a transmission storing module that stores the PDUs to which the RLC headers are added; a header field setting module that sets fields of the RLC headers in the PDUs received from the transmission storing module; and a ciphering module that ciphers the PDUs output from the header field setting module and then transmits the ciphered PDUs to a lower layer of the transmitting device, wherein the ciphering module checks D/C fields in the headers of the PDUs to determine whether the PDUs are data PDUs or control PDUs and ciphers the PDUs only if the PDUs are data PDUs, wherein the ciphering module ciphers piggybacked status PDUs in the data PDUs if the data PDUs include the piggybacked status PDUs.