997 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
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
On Low-Resolution ADCs in Practical 5G Millimeter-Wave Massive MIMO Systems
Nowadays, millimeter-wave (mmWave) massive multiple-input multiple-output
(MIMO) systems is a favorable candidate for the fifth generation (5G) cellular
systems. However, a key challenge is the high power consumption imposed by its
numerous radio frequency (RF) chains, which may be mitigated by opting for
low-resolution analog-to-digital converters (ADCs), whilst tolerating a
moderate performance loss. In this article, we discuss several important issues
based on the most recent research on mmWave massive MIMO systems relying on
low-resolution ADCs. We discuss the key transceiver design challenges including
channel estimation, signal detector, channel information feedback and transmit
precoding. Furthermore, we introduce a mixed-ADC architecture as an alternative
technique of improving the overall system performance. Finally, the associated
challenges and potential implementations of the practical 5G mmWave massive
MIMO system {with ADC quantizers} are discussed.Comment: to appear in IEEE Communications Magazin
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