Data communication method in mobile telecommunication system

PURPOSE: A data communication method for a mobile communication system is provided to efficiently use radio resources of a wireless system by combining MAC(Medium Access Control) SDUs(Service Data Units) into one during one TTI(Transmission Time Interval) and adding only one UE(User Equipment) ID during one TTI. CONSTITUTION: A specific protocol layer of a transmission side transmits a PDU(Protocol Data Unit) to a lower layer at a certain period through a common transport channel. The PDU has one header information and two or more upper PDUs. One header information includes a UE ID for identifying a UE. One header information includes a UE ID type indicator for informing the type of the UE ID.