Methods and devices for adjusting timing of uplink transmissions to a network node in a telecommunications system are provided. A user equipment (“UE”) is configurable with more than one aggregated serving cells that are divided into one or more groups of serving cells based on a timing advance value. The one or more groups of serving cells each comprises a timing reference serving cell. The reception timing of a downlink transmission from a timing reference serving cell is used as an uplink timing reference for the timing reference serving cell. The UE determines a change to a second timing reference serving cell and applies an incremental adjustment of the transmit timing of uplink transmissions for the serving cells in the group of serving cells with respect to a timing reference based on the reception timing of a downlink transmission from the second timing reference serving cell in the UE.