1,423 research outputs found
High-Rate Space Coding for Reconfigurable 2x2 Millimeter-Wave MIMO Systems
Millimeter-wave links are of a line-of-sight nature. Hence, multiple-input
multiple-output (MIMO) systems operating in the millimeter-wave band may not
achieve full spatial diversity or multiplexing. In this paper, we utilize
reconfigurable antennas and the high antenna directivity in the millimeter-wave
band to propose a rate-two space coding design for 2x2 MIMO systems. The
proposed scheme can be decoded with a low complexity maximum-likelihood
detector at the receiver and yet it can enhance the bit-error-rate performance
of millimeter-wave systems compared to traditional spatial multiplexing
schemes, such as the Vertical Bell Laboratories Layered Space-Time Architecture
(VBLAST). Using numerical simulations, we demonstrate the efficiency of the
proposed code and show its superiority compared to existing rate-two space-time
block codes
Reconfigurable Antennas in mmWave MIMO Systems
The key obstacle to achieving the full potential of the millimeter wave
(mmWave) band has been the poor propagation characteristics of wireless signals
in this band. One approach to overcome this issue is to use antennas that can
support higher gains while providing beam adaptability and diversity, i.e.,
reconfigurable antennas. In this article, we present a new architecture for
mmWave multiple-input multiple-output (MIMO) communications that uses a new
class of reconfigurable antennas. More specifically, the proposed lens-based
antennas can support multiple radiation patterns while using a single radio
frequency chain. Moreover, by using a beam selection network, each antenna beam
can be steered in the desired direction. Further, using the proposed
reconfigurable antenna in a MIMO architecture, we propose a new signal
processing algorithm that uses the additional degrees of freedom provided by
the antennas to overcome propagation issues at mmWave frequencies. Our
simulation results show that the proposed reconfigurable antenna MIMO
architecture significantly enhances the performance of mmWave communication
systems
Millimeter Wave Communications with Reconfigurable Antennas
The highly sparse nature of propagation channels and the restricted use of
radio frequency (RF) chains at transceivers limit the performance of millimeter
wave (mmWave) multiple-input multiple-output (MIMO) systems. Introducing
reconfigurable antennas to mmWave can offer an additional degree of freedom on
designing mmWave MIMO systems. This paper provides a theoretical framework for
studying the mmWave MIMO with reconfigurable antennas. We present an
architecture of reconfigurable mmWave MIMO with beamspace hybrid analog-digital
beamformers and reconfigurable antennas at both the transmitter and the
receiver. We show that employing reconfigurable antennas can provide throughput
gain for the mmWave MIMO. We derive the expression for the average throughput
gain of using reconfigurable antennas, and further simplify the expression by
considering the case of large number of reconfiguration states. In addition, we
propose a low-complexity algorithm for the reconfiguration state and beam
selection, which achieves nearly the same throughput performance as the optimal
selection of reconfiguration state and beams by exhaustive search.Comment: presented at IEEE ICC 201
Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays
Massive MIMO (multiple-input multiple-output) is no longer a "wild" or
"promising" concept for future cellular networks - in 2018 it became a reality.
Base stations (BSs) with 64 fully digital transceiver chains were commercially
deployed in several countries, the key ingredients of Massive MIMO have made it
into the 5G standard, the signal processing methods required to achieve
unprecedented spectral efficiency have been developed, and the limitation due
to pilot contamination has been resolved. Even the development of fully digital
Massive MIMO arrays for mmWave frequencies - once viewed prohibitively
complicated and costly - is well underway. In a few years, Massive MIMO with
fully digital transceivers will be a mainstream feature at both sub-6 GHz and
mmWave frequencies. In this paper, we explain how the first chapter of the
Massive MIMO research saga has come to an end, while the story has just begun.
The coming wide-scale deployment of BSs with massive antenna arrays opens the
door to a brand new world where spatial processing capabilities are
omnipresent. In addition to mobile broadband services, the antennas can be used
for other communication applications, such as low-power machine-type or
ultra-reliable communications, as well as non-communication applications such
as radar, sensing and positioning. We outline five new Massive MIMO related
research directions: Extremely large aperture arrays, Holographic Massive MIMO,
Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive
MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin
Design of Reconfigurable Multiple-Beam Array Feed Network Based on Millimeter-Wave Photonics Beamformers
In this chapter, elaborating the direction of designing photonics-based beamforming networks (BFN) for millimeter-wave (mmWave) antenna arrays, we review the worldwide progress referred to designing multiple-beam photonics BFN and highlight our last simulation results on design and optimization of millimeter-photonics-based matrix beamformers. In particular, we review the specialties of mmWave photonics technique in 5G mobile networks of Radio-over-Fiber (RoF) technology based on fiber-wireless architecture. In addition, the theoretical background of array antenna multiple-beam steering using ideal models of matrix-based phase shifters and time delay lines is presented including a general analysis of radiation pattern sensitivity to compare updated photonics beamforming networks produced on phase shifter or true-time delay approach. The principles and ways to optimized photonics BFN design are discussed based on the study of photonics BFN scheme including integrated 8×8 optical Butler matrix (OBM). All schemes are modeled using VPIphotonics Design Suite and MATLAB software tools. In the result of simulation experiments, the outcome is obtained that both the integrated optical Butler matrix itself and the BFN based on it possess an acceptable quality of beams formation in a particular 5G pico-cell
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