Beamforming in a Multi-Carrier OFDM System

MIMO and beamforming technologies are fundamental in current OFDM based 5G and coming 6G systems. When going to higher frequencies, the increased pathloss in the channel needs to be compensated with a larger antenna array to guarantee coverage. Todays systems deployed on midband spectrum (3–4GHz) is based on digital beamforming where complex weights are multiplied to QAM modulated symbols in OFDM frequency domain. When scaling up the array to compensate for the increased pathloss, this solution might be too complex. Turning to hybrid beamforming solutions could be one way to overcome the excessive increase in complexity. Using an analog beamforming step to reduce the dimensions is a common approach. This, however, will limit the performance of a multi-carrier system since all carriers will be spatially filtered by the same analog beamformer. In this talk we go through the pros and cons of different solutions and try to assess the impact on system capacity.