Episode 8: Analog versus Digital Beamforming

We have now released the eighth episode of the podcast Wireless Future, with the following abstract:

The new 5G millimeter wave systems make use of classical analog beamforming technology. It is often claimed that digital beamforming cannot be used in these bands due to its high energy consumption. In this episode, Erik G. Larsson and Emil Björnson are visited by Bengt Lindoff, Chief Systems Architect at the startup BeammWave. The conversation covers how fully digital beamforming solutions are now being made truly competitive and what this means for the future of wireless communications. To learn more about BeammWave’s hardware architecture visit https://www.beammwave.com/whitepapers.

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3 thoughts on “Episode 8: Analog versus Digital Beamforming”

  1. I don’t exactly recall where I heard this phrase, but I agree to its sentiment.

    “There is no Moore’s law for analogue”

    Looking back historically, a lot of radio-solutions has always started out as analogue, but over time shifted to digital solutions. In the early -00’s, people thought digital pre-distortion of power amplifiers was impossible due to the large oversampling – today it’s found in pretty much every single radio. The same thing with D/A-converters. A lot of hetero/homodyne radio transmitter designs are disappearing in favor of using high-speed DAC’s for direct-RF solutions. The border between digital and analogue is moving closer to the antenna every day!

  2. Thanks for your podcast. I have two questions about mmWave massive MIMO.

    1. Do you think it is necessary to adapt the transmit powers to small-scale fading variations in mmWave massive MIMO? Because the channels are highly correlated in mmWave, leading to a low level of channel hardening. The power optimization may not rely on the hardening bound instead the rigorous bound.

    2. For some well-adopted mmWave channel models, e.g., the extended Saleh-Valenzuela, it seems that more antennas in the BS cannot improve the level of channel hardening. As the channels are strongly spatially correlated from the antennas. Do you have any comments on this?

    Thanks in advance!

    1. 1. I suppose you have power allocation over the frequency domain in mind. The gain from that will depend on the channel model assumption and SNR. I would guess that a mmWave channel is dominated by a small number of strong paths, so that the frequency selectivity is rather small. But you can always compare equal power allocation and waterfilling to see how large the gap is in the setup that you consider.

      2. This depends on the assumptions that you are making when using the model, in particular, whether the rank of the correlation matrix grows with the number of antennas or not. Will adding more antennas lead to new propagation paths being discovered? Will it lead to an ability to distinguish between individual paths?

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