| 摘要 |
Introduction of a timing advance group concept into LTE TS 36.321 for release 11. A TA group comprises up to five cells. For each TA group the UE only needs a single TA timer. The initial timing alignment is achieved by a base station initiated RACH procedure. The BTS sends its initiation command on PDCCH. The TA command is a MAC element that comprises a 2 bit TA group index. A base station transmits control message(s) (1200) to assign each of secondary cells to a cell group in a plurality of cell groups comprising a primary cell group and a secondary cell group. The base the base station transmits a control command to the wireless device. The control command (1202) is configurable to cause transmission of a first random access preamble on a secondary cell in the secondary cell group. The control command is configurable to cause transmission of a second random access preamble on any secondary cell in the primary cell group. |
