Inter-CoMP cell interference is reduced by “extending” at least one CoMP cell to include UEs served by a neighboring CoMP cell in the extended CoMP cell's transmission calculations, so as to minimize interference to the UEs served by other CoMP cells. Each UE in a border sub-cell identifies neighboring CoMP cells from which it receives interference in excess of a threshold value, and includes the interfering CoMP cells in a close-neighbor set. The close-neighbor set is transmitted to the UE's serving CoMP cell controller. When downlink transmissions are scheduled to the target UE, the controller notifies the neighboring CoMP cells in the close-neighbor set, identifying the target UE. Those CoMP cells then use information about the channel conditions from their transmit antennas to the target UE receive antennas to compute transmissions to UEs they serve, with the constraint that interference to the target UE is below a predetermined level.