12,616 research outputs found
Correlated noise in networks of gravitational-wave detectors: subtraction and mitigation
One of the key science goals of advanced gravitational-wave detectors is to
observe a stochastic gravitational-wave background. However, recent work
demonstrates that correlated magnetic fields from Schumann resonances can
produce correlated strain noise over global distances, potentially limiting the
sensitivity of stochastic background searches with advanced detectors. In this
paper, we estimate the correlated noise budget for the worldwide Advanced LIGO
network and conclude that correlated noise may affect upcoming measurements. We
investigate the possibility of a Wiener filtering scheme to subtract correlated
noise from Advanced LIGO searches, and estimate the required specifications. We
also consider the possibility that residual correlated noise remains following
subtraction, and we devise an optimal strategy for measuring astronomical
parameters in the presence of correlated noise. Using this new formalism, we
estimate the loss of sensitivity for a broadband, isotropic stochastic
background search using 1 yr of LIGO data at design sensitivity. Given our
current noise budget, the uncertainty with which LIGO can estimate energy
density will likely increase by a factor of ~4--if it is impossible to achieve
significant subtraction. Additionally, narrowband cross-correlation searches
may be severely affected at low frequencies f < 45 Hz without effective
subtraction.Comment: 16 pages, 8 figure
Phase Modulation for Discrete-time Wiener Phase Noise Channels with Oversampling at High SNR
A discrete-time Wiener phase noise channel model is introduced in which
multiple samples are available at the output for every input symbol. A lower
bound on the capacity is developed. At high signal-to-noise ratio (SNR), if the
number of samples per symbol grows with the square root of the SNR, the
capacity pre-log is at least 3/4. This is strictly greater than the capacity
pre-log of the Wiener phase noise channel with only one sample per symbol,
which is 1/2. It is shown that amplitude modulation achieves a pre-log of 1/2
while phase modulation achieves a pre-log of at least 1/4.Comment: To appear in ISIT 201
Capacity Outer Bound and Degrees of Freedom of Wiener Phase Noise Channels with Oversampling
The discrete-time Wiener phase noise channel with an integrate-and-dump
multi-sample receiver is studied.
A novel outer bound on the capacity with an average input power constraint is
derived as a function of the oversampling factor.
This outer bound yields the degrees of freedom for the scenario in which the
oversampling factor grows with the transmit power as .
The result shows, perhaps surprisingly, that the largest pre-log that can be
attained with phase modulation at high signal-to-noise ratio is at most .Comment: 5 pages, 1 figure, Submitted to Intern. Workshop Inf. Theory (ITW)
201
Capacity of SIMO and MISO Phase-Noise Channels with Common/Separate Oscillators
In multiple antenna systems, phase noise due to instabilities of the
radio-frequency (RF) oscillators, acts differently depending on whether the RF
circuitries connected to each antenna are driven by separate (independent)
local oscillators (SLO) or by a common local oscillator (CLO). In this paper,
we investigate the high-SNR capacity of single-input multiple-output (SIMO) and
multiple-output single-input (MISO) phase-noise channels for both the CLO and
the SLO configurations.
Our results show that the first-order term in the high-SNR capacity expansion
is the same for all scenarios (SIMO/MISO and SLO/CLO), and equal to , where stands for the SNR. On the contrary, the second-order
term, which we refer to as phase-noise number, turns out to be
scenario-dependent. For the SIMO case, the SLO configuration provides a
diversity gain, resulting in a larger phase-noise number than for the CLO
configuration. For the case of Wiener phase noise, a diversity gain of at least
can be achieved, where is the number of receive antennas. For
the MISO, the CLO configuration yields a higher phase-noise number than the SLO
configuration. This is because with the CLO configuration one can obtain a
coherent-combining gain through maximum ratio transmission (a.k.a. conjugate
beamforming). This gain is unattainable with the SLO configuration.Comment: IEEE Transactions on Communication
Upper Bound on the Capacity of Discrete-Time Wiener Phase Noise Channels
A discrete-time Wiener phase noise channel with an integrate-and-dump
multi-sample receiver is studied. An upper bound to the capacity with an
average input power constraint is derived, and a high signal-to-noise ratio
(SNR) analysis is performed. If the oversampling factor grows as
for , then the capacity pre-log is at
most at high SNR.Comment: 5 pages, 1 figure. To be presented at IEEE Inf. Theory Workshop (ITW)
201
On the Capacity of the Wiener Phase-Noise Channel: Bounds and Capacity Achieving Distributions
In this paper, the capacity of the additive white Gaussian noise (AWGN)
channel, affected by time-varying Wiener phase noise is investigated. Tight
upper and lower bounds on the capacity of this channel are developed. The upper
bound is obtained by using the duality approach, and considering a specific
distribution over the output of the channel. In order to lower-bound the
capacity, first a family of capacity-achieving input distributions is found by
solving a functional optimization of the channel mutual information. Then,
lower bounds on the capacity are obtained by drawing samples from the proposed
distributions through Monte-Carlo simulations. The proposed capacity-achieving
input distributions are circularly symmetric, non-Gaussian, and the input
amplitudes are correlated over time. The evaluated capacity bounds are tight
for a wide range of signal-to-noise-ratio (SNR) values, and thus they can be
used to quantify the capacity. Specifically, the bounds follow the well-known
AWGN capacity curve at low SNR, while at high SNR, they coincide with the
high-SNR capacity result available in the literature for the phase-noise
channel.Comment: IEEE Transactions on Communications, 201
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