4,616 research outputs found
A Generalized Framework on Beamformer Design and CSI Acquisition for Single-Carrier Massive MIMO Systems in Millimeter Wave Channels
In this paper, we establish a general framework on the reduced dimensional
channel state information (CSI) estimation and pre-beamformer design for
frequency-selective massive multiple-input multiple-output MIMO systems
employing single-carrier (SC) modulation in time division duplex (TDD) mode by
exploiting the joint angle-delay domain channel sparsity in millimeter (mm)
wave frequencies. First, based on a generic subspace projection taking the
joint angle-delay power profile and user-grouping into account, the reduced
rank minimum mean square error (RR-MMSE) instantaneous CSI estimator is derived
for spatially correlated wideband MIMO channels. Second, the statistical
pre-beamformer design is considered for frequency-selective SC massive MIMO
channels. We examine the dimension reduction problem and subspace (beamspace)
construction on which the RR-MMSE estimation can be realized as accurately as
possible. Finally, a spatio-temporal domain correlator type reduced rank
channel estimator, as an approximation of the RR-MMSE estimate, is obtained by
carrying out least square (LS) estimation in a proper reduced dimensional
beamspace. It is observed that the proposed techniques show remarkable
robustness to the pilot interference (or contamination) with a significant
reduction in pilot overhead
Quantum information processing with space-division multiplexing optical fibres
The optical fibre is an essential tool for our communication infrastructure
since it is the main transmission channel for optical communications. The
latest major advance in optical fibre technology is spatial division
multiplexing (SDM), where new fibre designs and components establish multiple
co-existing data channels based on light propagation over distinct transverse
optical modes. Simultaneously, there have been many recent developments in the
field of quantum information processing (QIP), with novel protocols and devices
in areas such as computing, communication and metrology. Here, we review recent
works implementing QIP protocols with SDM optical fibres, and discuss new
possibilities for manipulating quantum systems based on this technology.Comment: Originally submitted version. Please see published version for
improved layout, new tables and updated references following review proces
Beamspace Aware Adaptive Channel Estimation for Single-Carrier Time-varying Massive MIMO Channels
In this paper, the problem of sequential beam construction and adaptive
channel estimation based on reduced rank (RR) Kalman filtering for
frequency-selective massive multiple-input multiple-output (MIMO) systems
employing single-carrier (SC) in time division duplex (TDD) mode are
considered. In two-stage beamforming, a new algorithm for statistical
pre-beamformer design is proposed for spatially correlated time-varying
wideband MIMO channels under the assumption that the channel is a stationary
Gauss-Markov random process. The proposed algorithm yields a nearly optimal
pre-beamformer whose beam pattern is designed sequentially with low complexity
by taking the user-grouping into account, and exploiting the properties of
Kalman filtering and associated prediction error covariance matrices. The
resulting design, based on the second order statistical properties of the
channel, generates beamspace on which the RR Kalman estimator can be realized
as accurately as possible. It is observed that the adaptive channel estimation
technique together with the proposed sequential beamspace construction shows
remarkable robustness to the pilot interference. This comes with significant
reduction in both pilot overhead and dimension of the pre-beamformer lowering
both hardware complexity and power consumption.Comment: 7 pages, 3 figures, accepted by IEEE ICC 2017 Wireless Communications
Symposiu
Fundamental Limits in Correlated Fading MIMO Broadcast Channels: Benefits of Transmit Correlation Diversity
We investigate asymptotic capacity limits of the Gaussian MIMO broadcast
channel (BC) with spatially correlated fading to understand when and how much
transmit correlation helps the capacity. By imposing a structure on channel
covariances (equivalently, transmit correlations at the transmitter side) of
users, also referred to as \emph{transmit correlation diversity}, the impact of
transmit correlation on the power gain of MIMO BCs is characterized in several
regimes of system parameters, with a particular interest in the large-scale
array (or massive MIMO) regime. Taking the cost for downlink training into
account, we provide asymptotic capacity bounds of multiuser MIMO downlink
systems to see how transmit correlation diversity affects the system
multiplexing gain. We make use of the notion of joint spatial division and
multiplexing (JSDM) to derive the capacity bounds. It is advocated in this
paper that transmit correlation diversity may be of use to significantly
increase multiplexing gain as well as power gain in multiuser MIMO systems. In
particular, the new type of diversity in wireless communications is shown to
improve the system multiplexing gain up to by a factor of the number of degrees
of such diversity. Finally, performance limits of conventional large-scale MIMO
systems not exploiting transmit correlation are also characterized.Comment: 29 pages, 8 figure
A Novel Millimeter-Wave Channel Simulator and Applications for 5G Wireless Communications
This paper presents details and applications of a novel channel simulation
software named NYUSIM, which can be used to generate realistic temporal and
spatial channel responses to support realistic physical- and link-layer
simulations and design for fifth-generation (5G) cellular communications.
NYUSIM is built upon the statistical spatial channel model for broadband
millimeter-wave (mmWave) wireless communication systems developed by
researchers at New York University (NYU). The simulator is applicable for a
wide range of carrier frequencies (500 MHz to 100 GHz), radio frequency (RF)
bandwidths (0 to 800 MHz), antenna beamwidths (7 to 360 degrees for azimuth and
7 to 45 degrees for elevation), and operating scenarios (urban microcell, urban
macrocell, and rural macrocell), and also incorporates multiple-input
multiple-output (MIMO) antenna arrays at the transmitter and receiver. This
paper also provides examples to demonstrate how to use NYUSIM for analyzing
MIMO channel conditions and spectral efficiencies, which show that NYUSIM is an
alternative and more realistic channel model compared to the 3rd Generation
Partnership Project (3GPP) and other channel models for mmWave bands.Comment: 7 pages, 8 figures, in 2017 IEEE International Conference on
Communications (ICC), Paris, May 201
Orbital Angular Momentum-based Space Division Multiplexing for High-capacity Underwater Optical Communications
To increase system capacity of underwater optical communications, we employ
the spatial domain to simultaneously transmit multiple orthogonal spatial
beams, each carrying an independent data channel. In this paper, we multiplex
and transmit four green orbital angular momentum (OAM) beams through a single
aperture. Moreover, we investigate the degrading effects of
scattering/turbidity, water current, and thermal gradient-induced turbulence,
and we find that thermal gradients cause the most distortions and turbidity
causes the most loss. We show systems results using two different data
generation techniques, one at 1064 nm for 10-Gbit/s/beam and one at 520 nm for
1-Gbit/s/beam, we use both techniques since present data-modulation
technologies are faster for infrared (IR) than for green. For the higher-rate
link, data is modulated in the IR, and OAM imprinting is performed in the green
using a specially-designed metasurface phase mask. For the lower rates, a green
laser diode is directly modulated. Finally, we show that inter-channel
crosstalk induced by thermal gradients can be mitigated using multi-channel
equalisation processing.Comment: 26 pages, 5 figure
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