Adaptive Beamforming Assisted Decision Feedback Equalization for Millimeter Wave Receivers

Beamforming and equalization are two key, but power hungry functions, essential in a mm-wave receiver. This paper proposes the incorporation of null adaptation and beam steering into the beamformer in order to reduce the length of the time-domain equalizer. The adaptive beamformer spatially filters the received signal field by steering main beam towards the angle of arrival of desired signal and steering nulls towards the angle of arrival of strong multipath components, thereby reducing their adverse effects prior to the DFE. This, in turn, significantly reduces the complexity and hence the power consumption of the DFE. The development of this architecture is closely guided by hardware considerations; in particular, the spatial processing hardware is implemented in the analog baseband domain, while the feedback equalizer is implemented using mixed analog-digital hardware. Adaptation circuitry is implemented using mostly digital hardware. Using this technique, higher data rates can be supported with a given number of elements. Conversely, the number of antennas and/or equalizer taps may be decreased while meeting a given data rate target. Extensive simulations using real mm-wave channel models are presented to support these hypotheses.