The invention relates to method and apparatus for reconfiguring a MAC entity of a MAC layer of the apparatus receiving protocol data units from a mobile terminal via on uplink upon reconfiguration of the uplink channel. Further, the invention relates to methods and mobile terminals for triggering the transmission of a status report from an RLC entity configured for an uplink channel of a network element in a radio access network, as well as a method and terminal for configuring the MAC layer of the mobile terminal. In order to enable an efficient and fast generation of RLC status reports after an uplink channel reconfiguration the invention suggests new mechanisms to trigger the transmission of status reports upon uplink reconfiguration as well a new operation and configuration of radio access network elements and UEs upon uplink channel reconfiguration, in particular a transmission time interval (TTI) reconfiguration.