The number of transmit and receive antennas is being scaled up for the upcoming millimeter-wave massive multiple-input multiple-output (MIMO) based 5G open radio access network (O-RAN) to meet the demands of ever-growing data-hungry users This may lead to a large number of RF chains at the open radio units (O-RUs) resulting in higher operational and infrastructure costs. To address this problem, we consider a linear detector based massive MIMO receiver and propose a novel combining architecture for reducing the required number of RF chains. The proposed architecture ensures that if a suitable combining solution complements, we can achieve an error performance similar to that of the linear detector (say MMSE). Thereby, we proposed two feasible combining solutions that lead to an error performance close to that of the system utilizing a fully connected (FC) RF chain architecture (i.e., dedicated RF chain for each receive antenna). The same trend is observed for the sum rate as well.

https://ieeexplore.ieee.org/document/10008509