31,268 research outputs found
Improving detection of acoustic signals by means of a time and frequency multiple energy detectors
Standard energy detectors (ED) are optimum to detect unknown signals in presence of uncorrelated Gaussian noise. However, in real applications the signal duration and bandwidth are unpredictable and this fact can considerably degrade the detection performance if the appropriate observation vector length is not correctly selected. Therefore, a multiple energy detector (MED) structure is applied in the time as well as in the frequency domain and it is evaluated in real acoustic scenarios. The results obtained demonstrate the robustness of the MED structure and a performance improvement in comparison to the standard ED. © 2011 IEEE.Manuscript received March 01, 2011; revised May 26, 2011; accepted May 29, 2011. Date of publication June 07, 2011; date of current version June 17, 2011. This work was supported by the Spanish Administration and the FEDER Programme of the EC under Grant TEC 2008-02975, and by the Generalitat Valenciana under Grant PROMETEO/2010/040. The associate editor coordinating the review of this manuscript and approving it for publication was Dr. Saeed Sanei.Moragues Escrivá, J.; Serrano Cartagena, A.; Vergara DomÃnguez, L.; Gosálbez Castillo, J. (2011). Improving detection of acoustic signals by means of a time and frequency multiple energy detectors. IEEE Signal Processing Letters. 18(8):458-461. https://doi.org/10.1109/LSP.2011.2158644S45846118
Exploring a search for long-duration transient gravitational waves associated with magnetar bursts
Soft gamma repeaters and anomalous X-ray pulsars are thought to be magnetars,
neutron stars with strong magnetic fields of order --. These objects emit intermittent bursts
of hard X-rays and soft gamma rays. Quasiperiodic oscillations in the X-ray
tails of giant flares imply the existence of neutron star oscillation modes
which could emit gravitational waves powered by the magnetar's magnetic energy
reservoir. We describe a method to search for transient gravitational-wave
signals associated with magnetar bursts with durations of 10s to 1000s of
seconds. The sensitivity of this method is estimated by adding simulated
waveforms to data from the sixth science run of Laser Interferometer
Gravitational-wave Observatory (LIGO). We find a search sensitivity in terms of
the root sum square strain amplitude of for a half sine-Gaussian waveform with a central
frequency and a characteristic time . This corresponds to a gravitational wave energy of
, the same order of
magnitude as the 2004 giant flare which had an estimated electromagnetic energy
of , where is the distance to SGR 1806-20. We
present an extrapolation of these results to Advanced LIGO, estimating a
sensitivity to a gravitational wave energy of for a magnetar at a distance of .
These results suggest this search method can probe significantly below the
energy budgets for magnetar burst emission mechanisms such as crust cracking
and hydrodynamic deformation
Multiband Spectrum Access: Great Promises for Future Cognitive Radio Networks
Cognitive radio has been widely considered as one of the prominent solutions
to tackle the spectrum scarcity. While the majority of existing research has
focused on single-band cognitive radio, multiband cognitive radio represents
great promises towards implementing efficient cognitive networks compared to
single-based networks. Multiband cognitive radio networks (MB-CRNs) are
expected to significantly enhance the network's throughput and provide better
channel maintenance by reducing handoff frequency. Nevertheless, the wideband
front-end and the multiband spectrum access impose a number of challenges yet
to overcome. This paper provides an in-depth analysis on the recent
advancements in multiband spectrum sensing techniques, their limitations, and
possible future directions to improve them. We study cooperative communications
for MB-CRNs to tackle a fundamental limit on diversity and sampling. We also
investigate several limits and tradeoffs of various design parameters for
MB-CRNs. In addition, we explore the key MB-CRNs performance metrics that
differ from the conventional metrics used for single-band based networks.Comment: 22 pages, 13 figures; published in the Proceedings of the IEEE
Journal, Special Issue on Future Radio Spectrum Access, March 201
Stacking Gravitational Wave Signals from Soft Gamma Repeater Bursts
Soft gamma repeaters (SGRs) have unique properties that make them intriguing
targets for gravitational wave (GW) searches. They are nearby, their burst
emission mechanism may involve neutron star crust fractures and excitation of
quasi-normal modes, and they burst repeatedly and sometimes spectacularly. A
recent LIGO search for transient GW from these sources placed upper limits on a
set of almost 200 individual SGR bursts. These limits were within the
theoretically predicted range of some models. We present a new search strategy
which builds upon the method used there by "stacking" potential GW signals from
multiple SGR bursts. We assume that variation in the time difference between
burst electromagnetic emission and burst GW emission is small relative to the
GW signal duration, and we time-align GW excess power time-frequency tilings
containing individual burst triggers to their corresponding electromagnetic
emissions. Using Monte Carlo simulations, we confirm that gains in GW energy
sensitivity of N^{1/2} are possible, where N is the number of stacked SGR
bursts. Estimated sensitivities for a mock search for gravitational waves from
the 2006 March 29 storm from SGR 1900+14 are also presented, for two GW
emission models, "fluence-weighted" and "flat" (unweighted).Comment: 17 pages, 16 figures, submitted to PR
Proposed method for searches of gravitational waves from PKS 2155-304 and other blazar flares
We propose to search for gravitational waves from PKS 2155-304 as well as
other blazars. PKS 2155-304 emitted a long duration energetic flare in July
2006, with total isotropic equivalent energy released in TeV gamma rays of
approximately ergs. Any possible gravitational wave signals
associated with this outburst should be seen by gravitational wave detectors at
the same time as the electromagnetic signal. During this flare, the two LIGO
interferometers at Hanford and the GEO detector were in operation and
collecting data. For this search we will use the data from multiple
gravitational wave detectors. The method we use for this purpose is a coherent
network analysis algorithm and is called {\tt RIDGE}. To estimate the
sensitivity of the search, we perform numerical simulations. The sensitivity to
estimated gravitational wave energy at the source is about
ergs for a detection probability of 20%. For this search, an end-to-end
analysis pipeline has been developed, which takes into account the motion of
the source across the sky.Comment: 10 pages, 7 figures. Contribution to 12th Gravitational Wave Data
Analysis Workshop. Submitted to Classical and Quantum Gravity. Changes in
response to referee comment
Spectrum Sensing of DVB-T2 Signals in Multipath Channels for Cognitive Radio Networks
© 2018 VDE VERLAG GMBHIn this paper, spectrum sensing of digital video broadcasting-second generation terrestrial (DVB-T2) signals in different fading environments with energy detection (ED) is considered. ED is known to achieve an increased performance among low computational complexity detectors, but it is susceptible to noise uncertainty. By taking into consideration the edge pilot and scattered pilot periodicity in DVB-T2 signals, a low computational complex noise power estimator is proposed. It is shown analytically that the choice of detector depends on the environment, the detector requirements, the available prior knowledge and with the noise power estimator. Simulation confirm that with the noise power estimator, ED significantly outperforms the pilot correlation-based detectors. Simulation also show that the proposed scheme enables ED to obtain increased detection performance in fading channels
Spectrum Sensing of DVB-T2 Signals using a Low Computational Noise Power Estimation
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted ncomponent of this work in other works.Cognitive radio is a promising technology that answers the spectrum scarcity problem arising from the proliferation of wireless networks and mobile services. In this paper, spectrum sensing of digital video broadcasting-second generation terrestrial (DVB-T2) signals in AWGN, WRAN and COST207 multipath fading environment are considered. ED is known to achieve an increased performance among low computational complexity detectors, but it is susceptible to noise uncertainty. Taking into consideration the edge pilot and scattered pilot periodicity in DVB-T2 signals, a low computational noise power estimator is proposed. Analytical forms for the detector are derived. Simulation results show that with the noise power estimator, ED significantly outperforms the pilot correlation-based detectors. Simulation also show that the proposed scheme enables ED to obtain increased detection performance in multi-path fading environments. Moreover, based on this algorithm a practical sensing scheme for cognitive radio networks is proposed.Peer reviewedFinal Accepted Versio
First joint search for gravitational-wave bursts in LIGO and GEO600 data
We present the results of the first joint search for gravitational-wave
bursts by the LIGO and GEO600 detectors. We search for bursts with
characteristic central frequencies in the band 768 to 2048 Hz in the data
acquired between the 22nd of February and the 23rd of March, 2005 (fourth LSC
Science Run - S4). We discuss the inclusion of the GEO600 data in the
Waveburst-CorrPower pipeline that first searches for coincident excess power
events without taking into account differences in the antenna responses or
strain sensitivities of the various detectors. We compare the performance of
this pipeline to that of the coherent Waveburst pipeline based on the maximum
likelihood statistic. This likelihood statistic is derived from a coherent sum
of the detector data streams that takes into account the antenna patterns and
sensitivities of the different detectors in the network. We find that the
coherentWaveburst pipeline is sensitive to signals of amplitude 30 - 50%
smaller than the Waveburst-CorrPower pipeline. We perform a search for
gravitational-wave bursts using both pipelines and find no detection candidates
in the S4 data set when all four instruments were operating stably.Comment: 30 pages, 8 figure
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