2,268 research outputs found
A Comparison of Hybrid Beamforming and Digital Beamforming with Low-Resolution ADCs for Multiple Users and Imperfect CSI
For 5G it will be important to leverage the available millimeter wave
spectrum. To achieve an approximately omni- directional coverage with a similar
effective antenna aperture compared to state of the art cellular systems, an
antenna array is required at both the mobile and basestation. Due to the large
bandwidth and inefficient amplifiers available in CMOS for mmWave, the analog
front-end of the receiver with a large number of antennas becomes especially
power hungry. Two main solutions exist to reduce the power consumption: hybrid
beam forming and digital beam forming with low resolution Analog to Digital
Converters (ADCs). In this work we compare the spectral and energy efficiency
of both systems under practical system constraints. We consider the effects of
channel estimation, transmitter impairments and multiple simultaneous users.
Our power consumption model considers components reported in literature at 60
GHz. In contrast to many other works we also consider the correlation of the
quantization error, and generalize the modeling of it to non-uniform quantizers
and different quantizers at each antenna. The result shows that as the SNR gets
larger the ADC resolution achieving the optimal energy efficiency gets also
larger. The energy efficiency peaks for 5 bit resolution at high SNR, since due
to other limiting factors the achievable rate almost saturates at this
resolution. We also show that in the multi-user scenario digital beamforming is
in any case more energy efficient than hybrid beamforming. In addition we show
that if different ADC resolutions are used we can achieve any desired
trade-offs between power consumption and rate close to those achieved with only
one ADC resolution.Comment: Submitted to JSTSP. arXiv admin note: text overlap with
arXiv:1610.0290
Low Power Analog-to-Digital Conversion in Millimeter Wave Systems: Impact of Resolution and Bandwidth on Performance
The wide bandwidth and large number of antennas used in millimeter wave
systems put a heavy burden on the power consumption at the receiver. In this
paper, using an additive quantization noise model, the effect of analog-digital
conversion (ADC) resolution and bandwidth on the achievable rate is
investigated for a multi-antenna system under a receiver power constraint. Two
receiver architectures, analog and digital combining, are compared in terms of
performance. Results demonstrate that: (i) For both analog and digital
combining, there is a maximum bandwidth beyond which the achievable rate
decreases; (ii) Depending on the operating regime of the system, analog
combiner may have higher rate but digital combining uses less bandwidth when
only ADC power consumption is considered, (iii) digital combining may have
higher rate when power consumption of all the components in the receiver
front-end are taken into account.Comment: 8 pages, 6 figures, in Proc. of IEEE Information Theory and
Applications Workshop, Feb. 201
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