Low-complexity hybrid precoding for energy-efficient mmWave transmission

Abstract

It is necessary to optimize the energy-efficient (EE) performance for millimeter-wave (mmWave) wireless systems, since the power consumption problem becomes increasingly crucial at high frequency bands. In hybrid precoding mmWave systems, the EE-oriented optimized elements include the analog and digital precoders at the transmitter, the analog and digital combiners at the receiver, as well as the corresponding number of opened radio frequency (RF) chains. In contrary to calculate the optimal precoding/combining matrices exhaustively for all possible numbers of RF chains as in the existing works, this paper proposes a two-stage alternative method with nearly optimal sum rate performance and much lower computation complexity. It firstly calculates the optimal number of opened RF chains, and then the nearly optimal precoder and combiner are directly obtained within only one round calculation. The complicated calculations of all the elements in optimization are decoupled by exploring the asymptotical property of the mmWave system with large antenna arrays, as well as the sparsity characteristic of the mmWave fading channel. Simulation results are further provided to verify the validation of the proposed method.