A wireless device receives at least one message comprising configuration parameters of a plurality of cells grouped into a plurality of timing advance groups (TAGs). A TAG is configurable to consist of one or more downlink-only cells if the wireless device has a first capability, otherwise each TAG comprises one or more downlink-uplink cells. The wireless device receives at least one timing advance command (TAC) for a first TAG. The wireless device applies the TAC to uplink transmission timing of at least one downlink-uplink cell in the first TAG.