Distributed MMSE Beamforming Design for Relay-Assisted C-RAN

In this paper, the linear minimum mean square error beamformers are designed for relay-assisted cloud radio access network (C-RAN). In C-RAN, the remote radio units are separated from the baseband units to save energy cost. To further enhance network coverage, it is a good choice to duly arrange relay nodes. Regrading the per-antenna power constraints at both the relay nodes and the remote radio heads (RRHs), the beamformer matrices at the relay nodes and RRHs are jointly optimized for the relay assisted C-RAN. Since the considered problem is a non-convex optimization problem and is with multiple variables, it is in general very hard to solve. To make the design suitable for C-RAN exploiting the problem structure, two novel decomposition algorithms are proposed. One algorithm is mainly carried out at the RRHs, another is mainly performed at the relay node. Finally in the simulations, the performance of the proposed algorithms are demonstrated.