50,026 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
Maximum Throughput Scheduling for Multi-connectivity in Millimeter-Wave Networks
Multi-connectivity is emerging as promising solution to provide reliable
communications and seamless connectivity at the millimeter-wave frequency
range. Due to the obstacles that cause frequent interruptions at such high
frequency range, connectivity to multiple cells can drastically increase the
network performance in terms of throughput and reliability by coordination
among the network elements. In this paper, we propose an algorithm for the link
scheduling optimization that maximizes the network throughput for
multi-connectivity in millimeter-wave cellular networks. The considered
approach exploits a centralized architecture, fast link switching, proactive
context preparation and data forwarding between millimeter-wave access points
and the users. The proposed algorithm is able to numerically approach the
global optimum and to quantify the potential gain of multi-connectivity in
millimeter-wave cellular networks
Millimeter-wave high-gain SIW end-fire bow-tie antenna
This communication presents a high-gain bow-tie antenna that operates across 57–64 GHz for application in high data rate point-to-point communication systems. The proposed antenna consists of a pair of bow-tie radiators, where each radiator is etched on the opposite side of the common dielectric substrate and fed through substrate integrated waveguide (SIW) feed-line. The bow-tie radiators are arranged to cross each other symmetrically by tilting the feed-lines by 30◦ to enhance the antenna gain and to obtain the required radiation pattern. The antenna is loaded with a pair of double G-shaped resonators (DGRs) that are located in a region between the radiators and SIW to suppress the back-lobe level in the H-plane. Embedded in the E-plane of the antenna is an array of zero index metamaterial (ZIM) unit-cells whose purpose is to effectively confine the electromagnetic waves in the end-fire direction to enhance its gain performance. A prototype antenna was fabricated and its performance was measured to validate the simulation results. The proposed structure exhibits a gain of 11.8–12.5 dBi over the frequency range of 57–64 GHz with reflection coefficient less than −11 dB. In addition, the proposed antenna exhibits good cross-polarization, which is less than −17 dB in both E- and H-planes at 60 GHz
Millimeter-wave studies
Progress on millimeter-wave propagation experiments in Hawaii is reported. A short path for measuring attenuation in rain at 9.6, 28.8, 57.6, and 96.1 GHz is in operation. A slant path from Hilo to the top of Mauna Kea is scheduled. On this path, scattering from rain and clouds that may cause interference for satellites closely spaced in geosynchronous orbit will be measured at the same frequencies at 28.8 and 96.1 GHz. In addition the full transmission matrix will be measured at the same frequencies on the slant path. The technique and equipment used to measure the transmission matrix are described
Millimeter-wave antenna system
Parabolic reflectors fabricated from Carbon Fiber Reinforced Plastic (CFRP) composite material will not distort their shape by more than 3 percent of millimeter wavelength, despite large temperature differences on reflector surfaces. CFRP has zero thermal expansion. It is derived from charred polyacrylonitrite plastic filaments that are combined with epoxy resin
Stochastic Geometry Modeling and Performance Evaluation of mmWave Cellular Communications
In this paper, a new mathematical framework to the analysis of millimeter
wave cellular networks is introduced. Its peculiarity lies in considering
realistic path-loss and blockage models, which are derived from experimental
data recently reported in the literature. The path-loss model accounts for
different distributions for line-of-sight and non-line-of-sight propagation
conditions and the blockage model includes an outage state that provides a
better representation of the outage possibilities of millimeter wave
communications. By modeling the locations of the base stations as points of a
Poisson point process and by relying upon a noise-limited approximation for
typical millimeter wave network deployments, exact integral expressions for
computing the coverage probability and the average rate are obtained. With the
aid of Monte Carlo simulations, the noise-limited approximation is shown to be
sufficiently accurate for typical network densities. Furthermore, it is shown
that sufficiently dense millimeter wave cellular networks are capable of
outperforming micro wave cellular networks, both in terms of coverage
probability and average rate.Comment: Presented at 2015 IEEE International Conference on Communications
(ICC), London, UK (June 2015). arXiv admin note: substantial text overlap
with arXiv:1410.357
Very compact millimeter sizes for composite star-forming/AGN submillimeter galaxies
We report the study of far-IR sizes of submillimeter galaxies (SMGs) in
relation to their dust-obscured star formation rate (SFR) and active galactic
nuclei (AGN) presence, determined using mid-IR photometry. We determined the
millimeter-wave (m) sizes of 69 ALMA-identified
SMGs, selected with confidence on ALMA images (--7.4 mJy). We found that all the SMGs are located above an
avoidance region in the millimeter size-flux plane, as expected by the
Eddington limit for star formation. In order to understand what drives the
different millimeter-wave sizes in SMGs, we investigated the relation between
millimeter-wave size and AGN fraction for 25 of our SMGs at --3. We found
that the SMGs for which the mid-IR emission is dominated by star formation or
AGN have extended millimeter-sizes, with respective median and 1.5 kpc. Instead, the SMGs for which
the mid-IR emission corresponds to star-forming/AGN composites have more
compact millimeter-wave sizes, with median
kpc. The relation between millimeter-wave size and AGN fraction suggests that
this size may be related to the evolutionary stage of the SMG. The very compact
sizes for composite star-forming/AGN systems could be explained by supermassive
black holes growing rapidly during the SMG coalescing, star-formation phase.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in ApJ Lette
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