24,148 research outputs found
Performance Analysis of Discrete Wavelet Multitone Transceiver for Narrowband PLC in Smart Grid
Smart Grid is an abstract idea, which involves the utilization of powerlines for sensing, measurement, control and communication for efficient utilization and distribution of energy, as well as automation of meter reading, load management and capillary control of Green Energy resources connected to the grid. Powerline Communication (PLC) has assumed a new role in the Smart Grid scenario, adopting the narrowband PLC (NB-PLC) for a low cost and low data rate communication for applications such as, automatic meter reading, dynamic management of load, etc. In this paper, we have proposed and simulated a discrete wavelet multitone (DWMT) transceiver in the presence of impulse noise for the NB-PLC channel applications in Smart Grid. The simulation results show that a DWMT transceiver outperforms a DFT-DMT with reference to the bit error rate (BER) performance
Acoustic Impulse Responses for Wearable Audio Devices
We present an open-access dataset of over 8000 acoustic impulse from 160
microphones spread across the body and affixed to wearable accessories. The
data can be used to evaluate audio capture and array processing systems using
wearable devices such as hearing aids, headphones, eyeglasses, jewelry, and
clothing. We analyze the acoustic transfer functions of different parts of the
body, measure the effects of clothing worn over microphones, compare
measurements from a live human subject to those from a mannequin, and simulate
the noise-reduction performance of several beamformers. The results suggest
that arrays of microphones spread across the body are more effective than those
confined to a single device.Comment: To appear at ICASSP 201
Infinite non-causality in active cancellation of random noise
Active cancellation of broadband random noise requires the detection of the
incoming noise with some time advance. In an duct for example this advance must
be larger than the delays in the secondary path from the control source to the
error sensor. In this paper it is shown that, in some cases, the advance
required for perfect noise cancellation is theoretically infinite because the
inverse of the secondary path, which is required for control, can include an
infinite non-causal response. This is shown to be the result of two mechanisms:
in the single-channel case (one control source and one error sensor), this can
arise because of strong echoes in the control path. In the multi-channel case
this can arise even in free field simply because of an unfortunate placing of
sensors and actuators. In the present paper optimal feedforward control is
derived through analytical and numerical computations, in the time and
frequency domains. It is shown that, in practice, the advance required for
significant noise attenuation can be much larger than the secondary path
delays. Practical rules are also suggested in order to prevent infinite
non-causality from appearing
Advanced Algorithms for Satellite Communication Signal Processing
Dizertační práce je zaměřena na softwarově definované přijímače určené k úzkopásmové družicové komunikaci. Komunikační kanály družicových spojů zahrnujících komunikaci s hlubokým vesmírem jsou zatíženy vysokými úrovněmi šumu, typicky modelovaného AWGN, a silným Dopplerovým posuvem signálu způsobeným mimořádnou rychlostí pohybu objektu. Dizertační práce představuje možné postupy řešení výpočetně efektivní digitální downkonverze úzkopásmových signálů a systému odhadu kmitočtu nosné úzkopásmových signálů zatížených Dopplerovým posuvem v řádu násobků šířky pásma signálu. Popis navrhovaných algoritmů zahrnuje analytický postup jejich vývoje a tam, kde je to možné, i analytické hodnocení jejich chování. Algoritmy jsou modelovány v prostředí MATLAB Simulink a tyto modely jsou využity pro ověření vlastností simulacemi. Modely byly také využity k experimentálním testům na reálném signálu přijatém z družice PSAT v laboratoři experimentálních družic na ústavu radioelektroniky.The dissertation is focused on software defined receivers intended for narrowband satellite communication. The satellite communication channel including deep space communication suffers from a high level of noise, typically modeled by AWGN, and from a strong Doppler shift of a signal caused by the unprecedented speed of an object in motion. The dissertation shows possible approaches to the issues of computationally efficient digital downconversion of narrowband signals and the carrier frequency estimation of narrowband signals distorted by the Doppler shift in the order of multiples of the signal bandwidth. The description of the proposed algorithms includes an analytical approach of its development and, if possible, the analytical performance assessment. The algorithms are modeled in MATLAB Simulink and the models are used for validating the performance by the simulation. The models were also used for experimental tests on the real signal received from the PSAT satellite at the laboratory of experimental satellites at the department of radio electronics.
Structured Sparsity Models for Multiparty Speech Recovery from Reverberant Recordings
We tackle the multi-party speech recovery problem through modeling the
acoustic of the reverberant chambers. Our approach exploits structured sparsity
models to perform room modeling and speech recovery. We propose a scheme for
characterizing the room acoustic from the unknown competing speech sources
relying on localization of the early images of the speakers by sparse
approximation of the spatial spectra of the virtual sources in a free-space
model. The images are then clustered exploiting the low-rank structure of the
spectro-temporal components belonging to each source. This enables us to
identify the early support of the room impulse response function and its unique
map to the room geometry. To further tackle the ambiguity of the reflection
ratios, we propose a novel formulation of the reverberation model and estimate
the absorption coefficients through a convex optimization exploiting joint
sparsity model formulated upon spatio-spectral sparsity of concurrent speech
representation. The acoustic parameters are then incorporated for separating
individual speech signals through either structured sparse recovery or inverse
filtering the acoustic channels. The experiments conducted on real data
recordings demonstrate the effectiveness of the proposed approach for
multi-party speech recovery and recognition.Comment: 31 page
Identification of Parametric Underspread Linear Systems and Super-Resolution Radar
Identification of time-varying linear systems, which introduce both
time-shifts (delays) and frequency-shifts (Doppler-shifts), is a central task
in many engineering applications. This paper studies the problem of
identification of underspread linear systems (ULSs), whose responses lie within
a unit-area region in the delay Doppler space, by probing them with a known
input signal. It is shown that sufficiently-underspread parametric linear
systems, described by a finite set of delays and Doppler-shifts, are
identifiable from a single observation as long as the time bandwidth product of
the input signal is proportional to the square of the total number of delay
Doppler pairs in the system. In addition, an algorithm is developed that
enables identification of parametric ULSs from an input train of pulses in
polynomial time by exploiting recent results on sub-Nyquist sampling for time
delay estimation and classical results on recovery of frequencies from a sum of
complex exponentials. Finally, application of these results to super-resolution
target detection using radar is discussed. Specifically, it is shown that the
proposed procedure allows to distinguish between multiple targets with very
close proximity in the delay Doppler space, resulting in a resolution that
substantially exceeds that of standard matched-filtering based techniques
without introducing leakage effects inherent in recently proposed compressed
sensing-based radar methods.Comment: Revised version of a journal paper submitted to IEEE Trans. Signal
Processing: 30 pages, 17 figure
Active control of sound inside a sphere via control of the acoustic pressure at the boundary surface
Here we investigate the practical feasibility of performing soundfield
reproduction throughout a three-dimensional area by controlling the acoustic
pressure measured at the boundary surface of the volume in question. The main
aim is to obtain quantitative data showing what performances a practical
implementation of this strategy is likely to yield. In particular, the
influence of two main limitations is studied, namely the spatial aliasing and
the resonance problems occurring at the eigenfrequencies associated with the
internal Dirichlet problem. The strategy studied is first approached by
performing numerical simulations, and then in experiments involving active
noise cancellation inside a sphere in an anechoic environment. The results show
that noise can be efficiently cancelled everywhere inside the sphere in a wide
frequency range, in the case of both pure tones and broadband noise, including
cases where the wavelength is similar to the diameter of the sphere. Excellent
agreement was observed between the results of the simulations and the
measurements. This method can be expected to yield similar performances when it
is used to reproduce soundfields.Comment: 28 pages de text
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