In a network (500) that provides high-speed packet access, a mobile terminal (510) is served by multiple activated serving cells (520) which are grouped into cell groups. The mobile terminal monitors control channel transmissions to detect whether there are any transmissions for the mobile terminal from the activated serving cells for each cell group and provides feedback to a primary serving cell. When no transmission is detected from serving cells of a particular cell group, the mobile terminal may transmit feedback information explicitly indicating that no transmission is detected for that cell group. Alternatively, the mobile terminal may withhold transmitting feedback for that cell group and increases the power for transmitting the feedback information for cell groups in which transmissions were detected.