An apparatus processes a first data packet header element of fixed length which identifies a bearer or a logical channel, as well as a configuration parameter indicating the length of an additional second data packet header element inclusive of a length of zero. A combination of the first data packet header element and the second data packet header element identifies a bearer or a logical channel of a user equipment. Data of different user equipments is processed in a transport block data packet by utilizing a packet header of the transport block data packet including combination of the first data packet header element and the second data packet header element for each different combination of bearer or logical channel and user equipment.