Uplink transmission method and apparatus in carrier aggregation system

The method according to claim I, wherein the selecting, under a preset reference carrier selection rule, one of downlink carriers corresponding to cells having already established downlink synchronization with a base station as a timing reference downlink carrier used by a secondary cell comprises:

• the user equipment selecting a timing reference downlink carrier used by a cell which is in a Timing Advance (TA) group to which the secondary cell belongs and has already established uplink synchronization with the base station as a timing reference downlink carrier used by the secondary cell;
• or
• the user equipment selecting a downlink component carrier corresponding to a cell the last to initiate a random access successfully in a TA group to which the secondary cell belongs as a timing reference downlink carrier used by the secondary cell;
• or
• the user equipment selecting a downlink component carrier corresponding to an active cell with the lowest number in a TA group to which the secondary cell belongs as a timing reference downlink carrier used by the secondary cell;
• or
• the user equipment selecting a downlink carrier corresponding to a primary cell as a timing reference downlink carrier used by the secondary cell;
• or
• the user equipment selecting a downlink carrier corresponding to the secondary cell as a timing reference downlink carrier used by the secondary cell;
• or
• the user equipment selecting a downlink carrier corresponding to a cell which is beyond a TA group to which the secondary cell belongs and has already established uplink synchronization with the base station as a timing reference downlink carrier used by the secondary cell;
• or
• the user equipment selecting a downlink carrier corresponding to a cell preconfigured by the base station as a timing reference downlink carrier used by the secondary cell.

The user equipment according to claim S. wherein the reference carrier determination unit is configured:

• to select a timing reference downlink carrier used by a cell which is in a Timing Advance (TA) group to which the secondary cell belongs and has already established uplink synchronization with the base station as a timing reference downlink carrier used by the secondary cell;
• or
• to select a downlink component carrier corresponding to a cell the last to initiate a random access successfully in a TA group to which the secondary cell belongs as a timing reference downlink carrier used by the secondary cell;
• or
• to select a downlink component carrier corresponding to an active cell with the lowest number in a TA group to which the secondary cell belongs as a timing reference downlink carrier used by the secondary cell;
• or
• to select a downlink carrier corresponding to a primary cell as a tuning reference downlink carrier used by the secondary cell;
• or
• to select a downlink carrier corresponding to the secondary cell as a timing reference downlink carrier used by the secondary cell;
• or
• to select a downlink carrier corresponding to a cell which is beyond a TA group to which the secondary cell belongs and has already established uplink synchronization with the base station as a timing reference downlink carrier used by the secondary cell;
• or
• to select a downlink carrier corresponding to a cell preconfigured by the base station as a timing reference downlink carrier used by the secondary cell.