1. A method comprising:receiving at least one message comprising configuration parameters of a plurality of cells, wherein:
the plurality of cells are grouped into a plurality of timing advance groups (TAGs); and
the plurality of cells comprise:
a primary cell with a primary physical uplink control channel (PUCCH); and
a PUCCH secondary cell with a secondary PUCCH, wherein the PUCCH secondary cell is in a first TAG in the plurality of TAGs;
receiving, in a first subframe, a random access response comprising a timing advance command (TAC) associated with the first TAG;
starting transmission of uplink signals via the first TAG on or before a second subframe that is four subframes after the first subframe; and
starting transmission of valid channel state information (CSI) via the PUCCH secondary cell on or after a third subframe that is six subframes after the first subframe.