A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes transmitting the UECapabilityInformation to the base station, receiving a RRCReconfiguration from the base station, receiving a PDCCH order from the base station, transmitting a preamble to the base station based on the PDCCH order, receiving a response from the base station and determining Timing advance between downlink and uplink (TTA). If the type1 PDCCH order was received, the terminal determining TTA of a first cell based on the first field (TAC) and the subcarrier spacing for a first PUSCH transmission. The first cell is the cell where the first PDCCH order was received. If the type2 PDCCH order was received, the terminal determining TTA of a second cell based on the first field and the subcarrier spacing for the preamble transmission and the second field (CMG identifier).