939 research outputs found
5G Millimeter Wave Cellular System Capacity with Fully Digital Beamforming
Due to heavy reliance of millimeter-wave (mmWave) wireless systems on
directional links, Beamforming (BF) with high-dimensional arrays is essential
for cellular systems in these frequencies. How to perform the array processing
in a power efficient manner is a fundamental challenge. Analog and hybrid BF
require fewer analog-to-digital converters (ADCs), but can only communicate in
a small number of directions at a time,limiting directional search, spatial
multiplexing and control signaling. Digital BF enables flexible spatial
processing, but must be operated at a low quantization resolution to stay
within reasonable power levels. This paper presents a simple additive white
Gaussian noise (AWGN) model to assess the effect of low resolution quantization
of cellular system capacity. Simulations with this model reveal that at
moderate resolutions (3-4 bits per ADC), there is negligible loss in downlink
cellular capacity from quantization. In essence, the low-resolution ADCs limit
the high SNR, where cellular systems typically do not operate. The findings
suggest that low-resolution fully digital BF architectures can be power
efficient, offer greatly enhanced control plane functionality and comparable
data plane performance to analog BF.Comment: To appear in the Proceedings of the 51st Asilomar Conference on
Signals, Systems, and Computers, 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
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