38,054 research outputs found
Multiuser Detection For Asynchronous ARGOS Signals
In this paper, we investigate the application of multiuser detection techniques to a Low Polar Orbit (LPO) mobile satellite used in the ARGOS system. These techniques are used to mitigate the multiple access interference in the uplink transmission of the system. Unlike CDMA, due to the Doppler Effect, each signal has a different received carrier frequency and a different propagation delay. Multiuser detection techniques are proposed for asynchronous
transmission in ARGOS system: the maximum likelihood detector, the conventional detector, and the sequential
interference cancellation detector, as solutions to tackle the interference effects. Bit Error Rate performance graphs are shown for these techniques
PPM demodulation: On approaching fundamental limits of optical communications
We consider the problem of demodulating M-ary optical PPM (pulse-position
modulation) waveforms, and propose a structured receiver whose mean probability
of symbol error is smaller than all known receivers, and approaches the quantum
limit. The receiver uses photodetection coupled with optimized phase-coherent
optical feedback control and a phase-sensitive parametric amplifier. We present
a general framework of optical receivers known as the conditional pulse nulling
receiver, and present new results on ultimate limits and achievable regions of
spectral versus photon efficiency tradeoffs for the single-spatial-mode
pure-loss optical communication channel.Comment: 5 pages, 6 figures, IEEE ISIT, Austin, TX (2010
Task-Driven Adaptive Statistical Compressive Sensing of Gaussian Mixture Models
A framework for adaptive and non-adaptive statistical compressive sensing is
developed, where a statistical model replaces the standard sparsity model of
classical compressive sensing. We propose within this framework optimal
task-specific sensing protocols specifically and jointly designed for
classification and reconstruction. A two-step adaptive sensing paradigm is
developed, where online sensing is applied to detect the signal class in the
first step, followed by a reconstruction step adapted to the detected class and
the observed samples. The approach is based on information theory, here
tailored for Gaussian mixture models (GMMs), where an information-theoretic
objective relationship between the sensed signals and a representation of the
specific task of interest is maximized. Experimental results using synthetic
signals, Landsat satellite attributes, and natural images of different sizes
and with different noise levels show the improvements achieved using the
proposed framework when compared to more standard sensing protocols. The
underlying formulation can be applied beyond GMMs, at the price of higher
mathematical and computational complexity
Performance of optimum detector structures for noisy intersymbol interference channels
The errors which arise in transmitting digital information by radio or wireline systems because of additive noise from successively transmitted signals interfering with one another are described. The probability of error and the performance of optimum detector structures are examined. A comparative study of the performance of certain detector structures and approximations to them, and the performance of a transversal equalizer are included
Three-way noiseless signal splitting in a parametric amplifier with quantum correlation
We demonstrate that a phase-insensitive parametric amplifier, coupled to a
quantum correlated source, can be used as a quantum information tap for
noiseless three-way signal splitting. We find that the output signals are
amplified noiselessly in two of the three output ports while the other can more
or less keep its original input size without adding noise. This scheme is able
to cascade and scales up for efficient information distribution in an optical
network. Furthermore, we find this scheme satisfies the criteria for a
non-ideal quantum non-demolition (QND) measurement and thus can serve as a QND
measurement device. With two readouts correlated to the input, we find this
scheme also satisfies the criterion for sequential QND measurement
Sequential projection pursuit for optimal transformation of autoregressive coefficients for damage detection in an experimental wind turbine blade
Peer reviewedPublisher PD
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
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