A Practical Channel Estimation Scheme for Sub-Connected Hybrid Massive MIMO Systems

In massive multiple-input multiple-output (MIMO) system, the increasing number of antennas causes high power consumption and hardware complexity. Sub-connected hybrid system structure can effectively mitigate integration difficulty and reduce the number of radio frequency (RF) chains. Despite losing little degrees of freedom, this structure makes massive MIMO achieved in practice. In this paper, we proposes a uplink channel estimation scheme where a sub-connected hybrid massive MIMO base station (BS) communicates with a single-antenna user. Since the sparsity caused by severe path loss, channel state information can be reconstructed by estimating the angles and gains of paths. We apply joint beam selection and sum-difference beam (JBSSDB) method to estimate path angles and utilize least square (LS) method to estimate gains information. Simulation results demonstrate that the proposed scheme achieves lower NMSE than conventional method in the case of same overhead.