Method and apparatus for change of primary cell during carrier aggregation

A method in a base station for receiving uplink control information from a mobile station during carrier aggregation operation, the method comprising:

• the base station configuring a first uplink control channel for transmitting uplink control information from the mobile station to a first primary cell, the first primary cell being one of a first group of serving cells used in carrier aggregation communication between the base station and the mobile station:
• configuring one or more uplink shared channels for receiving uplink data;
• transmitting a message to the mobile station indicating a change of primary cell to a second primary cell, the second primary cell being one of a second group of serving cells used in carrier aggregation communication between the base station and the mobile station, wherein the message indicating the change of primary cell comprises at least one of configuration information for a second uplink control channel for transmitting uplink control information from the mobile station to the second primary cell and a new mobile station identifier;
• monitoring uplink control information from the mobile station exclusively on the one or more uplink shared channels;
• receiving via one or more of the uplink shared channels a message from the mobile station indicating successful change of the primary cell from the first primary cell to the second primary cell;
• and
• monitoring, in response to receiving the message from the mobile station indicating successful change of the primary cell, the second uplink control channel from the mobile station to the second primary cell.