Abstract:
In this paper, we consider the decode-and-forward (DF) relay system in millimeter-wave
(mmWave) massive multiple-input multiple-output (MIMO) systems, and propose a hybrid beamforming
design method for the mixed structure, which contains the fully-connected and sub-connected structures. To satisfy constant-modulus and block-diagonalization (BD) constraints, the analog beamforming is
designed by the idea of sorted successive interference cancellation (SSIC). More specifically, the proposed
method first sorts the capacities of different analog sub-channels in descending order, and then designs the
analog beamforming serially according to the order of the capacities. To efficiently mitigate the inner-user
and inter-user interference, we propose a modified baseband BD technology to reduce the information loss
in digital beamforming design, thereby improving the system capacity. In addition, the proposed hybrid
beamforming algorithm is designed by considering both uniform linear arrays (ULAs) and uniform planar
arrays (UPAs). Simulation results demonstrate that the proposed hybrid beamforming design scheme can
obtain good performance in terms of the achievable sum-rate and power efficiency in ULAs and UPAs.