A method includes receiving in a mobile communication terminal signals from multiple cells that coordinate transmission of the signals with one another in a Cooperative Multipoint (CoMP) scheme. At least first and second Channel Quality Indicators (CQIs), for respective communication channels over which the signals are received, are calculated in the terminal based on the received signals. The second CQI is differentially encoded relative to the first CQI. Feedback information, including the first CQI and the differentially-encoded second CQI, is transmitted from the terminal.