Joint optimization of transmit and relay beamformer for single group multicast transmission

In this paper, single group multicasting is considered for the cooperative relay network. Two-phase transmission is performed and amplify-and-forward relay protocol is used. In the first phase, the base station broadcasts the common signal to the single antenna relays by employing beamforming. Each relay multiplies its received signal by a complex weight and retransmits it to the single antenna users. The aim is to find the beamformer weights at the base station and the relays jointly to minimize the total transmitted power while satisfying signal-to-noise ratio constraint for each user. Nonconvex joint problem is firstly relaxed and then converted to an equivalent biconvex problem by using exact penalty approach. The equivalent problem is solved iteratively using alternating minimization. To the best of our knowledge, this is the first work that considers joint beamforming at the base station and the relays for single group multicasting scenario.