36,853 research outputs found
Dense multiple antenna systems
We consider multiple antenna systems in which a large number of antennas occupy a given physical volume. In this regime the assumptions of the standard models of multiple antennas systems become questionable. We show that for such spatially dense multiple antenna systems one should expect the behavior of the capacity to be qualitatively different than what the standard multiple antenna models predict
Effects of Mutual Coupling on Degree of Freedom and Antenna Efficiency in Holographic MIMO Communications
The holographic multiple-input-multiple-output (MIMO) communications refer to
the MIMO systems built with ultra-dense antenna arrays, whose channel models
and potential applications have attracted increasing attentions recently. When
the spacing between adjacent array elements is larger than half wavelength, the
effect of mutual coupling can generally be neglected in current antenna
designs. However, in holographic MIMO communications, the influence of strong
mutual coupling on antenna characteristics is inevitable, resulting in
distorted radiation patterns and low radiation efficiencies. In this paper,
starting from the analytical correlation and efficiency models, we investigate
how the mutual coupling affects the capacity of a space-constrained MIMO system
from the aspects of degree of freedom (DOF) and antenna efficiency. The
involved fundamental concepts of correlation, DOF, efficiency and mutual
coupling are crucial for both antenna and wireless-communication engineers when
designing emerging MIMO communication systems
Impact of correlation and coupling on the capacity of MIMO systems
In this work, we consider the multiple antenna systems in which a large number of antennas occupy a given physical volume, and investigate the behavior of the capacity when increasing the number of antennas. In this regime the assumptions of the standard multiple antenna models become questionable. We introduce several new channel models that better fit this scenario and show that for such "spatially dense" multiple antenna systems, one should expect the behavior of the capacity to be qualitatively different than what the standard of multiple antenna models predict
Pulse Shaping Diversity to Enhance Throughput in Ultra-Dense Small Cell Networks
Spatial multiplexing (SM) gains in multiple input multiple output (MIMO)
cellular networks are limited when used in combination with ultra-dense small
cell networks. This limitation is due to large spatial correlation among
channel pairs. More specifically, it is due to i) line-of-sight (LOS)
communication between user equipment (UE) and base station (BS) and ii)
in-sufficient spacing between antenna elements. We propose to shape transmit
signals at adjacent antennas with distinct interpolating filters which
introduces pulse shaping diversity eventually leading to improved SINR and
throughput at the UEs. In this technique, each antenna transmits its own data
stream with a relative offset with respect to adjacent antenna. The delay which
must be a fraction of symbol period is interpolated with the pulse shaped
signal and generates a virtual MIMO channel that leads to improved diversity
and SINR at the receiver. Note that non-integral sampling periods with
inter-symbol interference (ISI) should be mitigated at the receiver. For this,
we propose to use a fractionally spaced equalizer (FSE) designed based on the
minimum mean squared error (MMSE) criterion. Simulation results show that for a
2x2 MIMO and with inter-site-distance (ISD) of 50 m, the median received SINR
and throughput at the UE improves by a factor of 11 dB and 2x, respectively,
which verifies that pulse shaping can overcome poor SM gains in ultra-dense
small cell networks.Comment: Accepted to 17th IEEE International Workshop on Signal Processing
Advances in Wireless Communication
Open-Loop Spatial Multiplexing and Diversity Communications in Ad Hoc Networks
This paper investigates the performance of open-loop multi-antenna
point-to-point links in ad hoc networks with slotted ALOHA medium access
control (MAC). We consider spatial multiplexing transmission with linear
maximum ratio combining and zero forcing receivers, as well as orthogonal space
time block coded transmission. New closed-form expressions are derived for the
outage probability, throughput and transmission capacity. Our results
demonstrate that both the best performing scheme and the optimum number of
transmit antennas depend on different network parameters, such as the node
intensity and the signal-to-interference-and-noise ratio operating value. We
then compare the performance to a network consisting of single-antenna devices
and an idealized fully centrally coordinated MAC. These results show that
multi-antenna schemes with a simple decentralized slotted ALOHA MAC can
outperform even idealized single-antenna networks in various practical
scenarios.Comment: 51 pages, 19 figures, submitted to IEEE Transactions on Information
Theor
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