A Low-Complexity Transmit Beamforming Scheme in Relayed Multicast Systems

In this work, we study the problem of maximizing the system throughput assuming a multicast system with a multi-antenna Base Station (BS) and one single-antenna relay. We employ two different transmission slots: one in which only the BS transmits and one in which only the relay transmits. Given the multi-antenna and multi-slot nature of the problem, transmit beamforming and diversity techniques can be employed. We present the optimization problem and a heuristic scheme is proposed to solve the problem with low computational complexity. Our solution iteratively combines the current precoder with the optimal precoder to the current worst User Equipment (UE). The results show that the beamforming gain outmatches the loss from the additional time slot in the proposed scheme and that it is capable of performing close to the optimum.