Cooperative beamforming for multiple multicast groups over multiple resource blocks

We consider beamforming for multicasting the same data from a single or cooperatively from multiple base stations (BS) to several user equipments (UE). BSs have uncorrelated antennas. Beamforming can be applied separately for each physical layer resource block (PRB) of 180kHz bandwidth. The channel is almost flat within a PRB but frequency selective across the PRBs within the system bandwidth. FEC extends over the entire system bandwidth. For each UE a metric of aggregate per-PRB SINR is calculated. The beamforming goal is to maximize the minimum metric of all UEs. Two algorithms for determining the beamforming weights are considered, one iterative algorithm based on signal and interference gradients and an algorithm based on semidefinite relaxation (SDR). Performance evaluation employs a 3GPP network deployment and channel models. Results show that the gradient based algorithm outperforms SDR in the single BS scenario. In the cooperative multi-BS scenario the SDR algorithm performs better.