The rest of the paper is organized as follows. In Section
II, the system model is presented and then the distributed
beamforming problem is formulated. In Section III, we first
study the case with single receive antenna at each relay,
and develop the SLIPD method from which Algorithm 1 is
designed for solving this problem, followed by a rigorous
convergence analysis. In Section IV, the SLIPD method is
extended to the more general case with multiple receive
antennas at each relay, and then Algorithm 2, a dual-layer
distributed algorithm, is presented with the aid of successive
convex approximations. Simulation results are presented to
support the efficacy of the proposed two algorithms in Section
V. Finally, some conclusions are provided in Section VI.