Cooperative Beamforming with Multiple Base Station Assignment Based on Correlation Knowledge

This paper presents a new approach for intercell interference mitigation with downlink beamforming based on long-term channel state information in a multiuser multicell scenario. In contrast to many previous downlink beamforming approaches, where a group of users is served by one base station (BS), this paper considers an assignment of multiple BSs to a group of users. Inside a user group, unicast transmission to scheduled users or multicast transmission to all users of this group can be applied. A solution based on semidefinite programming for the optimization of the beamforming weights is given and a comparison of the conventional beamforming with a single BS assignment and beamforming with multi-BSs assignment is presented for the two different transmission scenarios. Beamforming with multi-BS assignment outperforms the conventional beamforming with single BS assignment considering fairness among the users, but at the expense of a reduced sum rate in the case of a unicast transmission. An additional improvement of the throughput for users in the cell edge region can be observed.