433 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
Energy efficiency of mmWave massive MIMO precoding with low-resolution DACs
With the congestion of the sub-6 GHz spectrum, the interest in massive
multiple-input multiple-output (MIMO) systems operating on millimeter wave
spectrum grows. In order to reduce the power consumption of such massive MIMO
systems, hybrid analog/digital transceivers and application of low-resolution
digital-to-analog/analog-to-digital converters have been recently proposed. In
this work, we investigate the energy efficiency of quantized hybrid
transmitters equipped with a fully/partially-connected phase-shifting network
composed of active/passive phase-shifters and compare it to that of quantized
digital precoders. We introduce a quantized single-user MIMO system model based
on an additive quantization noise approximation considering realistic power
consumption and loss models to evaluate the spectral and energy efficiencies of
the transmit precoding methods. Simulation results show that
partially-connected hybrid precoders can be more energy-efficient compared to
digital precoders, while fully-connected hybrid precoders exhibit poor energy
efficiency in general. Also, the topology of phase-shifting components offers
an energy-spectral efficiency trade-off: active phase-shifters provide higher
data rates, while passive phase-shifters maintain better energy efficiency.Comment: Published in IEEE Journal of Selected Topics in Signal Processin
Context Information Based Initial Cell Search for Millimeter Wave 5G Cellular Networks
Millimeter wave (mmWave) communication is envisioned as a cornerstone to
fulfill the data rate requirements for fifth generation (5G) cellular networks.
In mmWave communication, beamforming is considered as a key technology to
combat the high path-loss, and unlike in conventional microwave communication,
beamforming may be necessary even during initial access/cell search. Among the
proposed beamforming schemes for initial cell search, analog beamforming is a
power efficient approach but suffers from its inherent search delay during
initial access. In this work, we argue that analog beamforming can still be a
viable choice when context information about mmWave base stations (BS) is
available at the mobile station (MS). We then study how the performance of
analog beamforming degrades in case of angular errors in the available context
information. Finally, we present an analog beamforming receiver architecture
that uses multiple arrays of Phase Shifters and a single RF chain to combat the
effect of angular errors, showing that it can achieve the same performance as
hybrid beamforming
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