Hybrid Beamforming Channel Estimation With Reduced Phase shifter numbers for Massive MIMO Systems

Abstract

A hybrid analog and digital beamforming structure has recently emerged as a promising technique to make low-cost large scale multiple-input-multiple-output (MIMO) communication systems. To decrease the power consumption and system complexity of hybrid beamforming structure, two subconnected analog beamforming methods are used: 1) with phase shifter, 2) and with fully-connected switch network. In the first method, a subconnected structure with phase shifter is used to reduce the computational complexity of fully connected hybrid beam-forming systems. Then, in the second method, to minimize power consumption of analog beamformer, a subconnected phase shifter structure is combined with a fully-connected switch network which reduces phase shifter upto 50%. In this paper, the impact of the channel estimation error (CEE) for the mentioned two hybrid beamforming structures on the effective spectral efficiency for a multi-user MIMO system with zero-forcing detection technique is investigated. Later, the variation in spectral efficiency of subconnected structure with phase shifter, and with fully-connected switch network is compared in presence of both perfect and imperfect channel state information (CSI). All the results are verified using computer simulations.