Adaptive Digital Beamforming for Uplink Coverage Enhancement in 5G NR System

Since the sub 6 GHz spectrum supports the cell capacity and coverage that can provide diverse services, most of the network operators chose the corresponding spectrum in the 5G initial deployment stage. The digital beamforming with cross polarized array antennas is a promising technique to provide high data rate and cell coverage enhancement in a sub 6 GHz 5G NR system. Unfortunately, the uplink coverage at sub 6 GHz is more challenging because the mobile station beamforming is not possible due to the limited hardware area for embedding massive antennas and transmit power of mobile station is limited. Particularly, the uplink channel quality deterioration causes downlink beamforming performance degradation in the time division duplex (TDD) mode because the fully digital beamforming performs the downlink beamforming weight decision through the uplink channel estimation. We proposed the adaptive digital beamforming based on Cross Polarized Array Antennas and analyzed the performance for uplink coverage of cell edge in the sub 6 GHz 5G NR system in this letter.