Wireless Mantra of the Week: Beamforming in NR

Mantra: 5G NR can make use of a variety of beamforming techniques such as digital beamforming, analog beamforming, and hybrid beamforming.
Brief Explanation. 4G LTE has traditionally used digital beamforming, where digital modulation symbols are transformed at the transmitter such that the receiver experiences a signal with higher signal strength and SINR. For example, one antenna port of the Base Station may send a modulation symbol X on subcarrier f1 and another antenna port may send -X (i.e., 180 degree phase shifted version of X) on the same subcarrier f1. If the transformation of the modulation symbol is appropriate, the receiver experiences higher signal strength and SINR. At higher frequencies such as millimeter wave frequencies, analog beamforming is more cost-effective and efficient, where amplitude and phase adjustments are made for numerous analog signals. While pure analog beamforming can provide a huge beamforming gain, it cannot support spatial multiplexing such as SU-MIMO. That’s where hybrid beamforming comes into the picture! Hybrid beamforming combines digital beamforming with analog beamforming and helps realize a good beamforming gain and supports spatial multiplexing.

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