Performance Evaluation of Space–Time Block Codes Over Keyhole Weibull Fading Channels

It is well known that degenerate channel phenomena known as keyholes may significantly reduce the capacity of multiple-input and multiple-output (mimo) channels. Keyhole mimo channels were predicted theoretically and also observed experimentally. In this paper, a novel method of analyzing the performance of keyhole mimo channels is proposed. The proposed method is based on the assumption that the received signal at the keyhole encompasses an arbitrary number of multipath components and the propagation environment is such that the resulting signal is observed as a non-linear function of the modulus of the sum of these components. Based on this assumption, we initially introduce the double Weibull fading model, constructed by the product of two independent Weibull distributed fading envelopes. Closed-form expressions for its moments-generating function, probability density function, cumulative distribution function, and moments are also derived. Based on these formulas, we analytically evaluate the performance of a 2 × 2 mimo space–time block-coding (stbc) system, where performance metrics such as the average symbol error probability for several modulation schemes, outage probability, amount of fading and ergodic capacity are given in closed form. Various performance evaluation results are presented in order to verify the proposed analysis.

Peculiar behavior of polysaccharide/borax hydrogel tablets: a dynamomechanical characterization

The peculiar unidirectional elongation observed during swelling of tablets prepared with scleroglucan (Sclg) and borax was compared with that of other synthetic and natural polymers capable of physical/chemical interactions with borate ions. A dynamomechanical characterization of “squared” Sclg/borax tablets was carried out to study the differences detectable on the two sides of the matrix corresponding to the two directions, respectively, the parallel and perpendicular one with respect to the applied compression force. Different compression forces were used and, in some cases, a second compression was applied on the tablets along a direction perpendicular to the first one. Birefringence experiments were carried out on the swelled tablets along the two directions. Obtained results allow correlating the anisotropic swelling behavior with the detected dynamomechanical and optical properties of the Sclg/borax system. Among the various tested polymers, only guar gum and, to a lesser extent, locust bean gum, showed an anisotropic elongation during swelling.     

Locally optimum Bayes detection in ergodic Markov noise

The locally optimum Bayes theory of signal detection in non-Gaussian noise/interference environments is extended to include ergodic Markov noise models under mild regularity assumptions on the conditional probability density functions. The proposed method expresses the log-likelihood ratio under the null hypothesis, via martingale limit theory, as a locally asymptotically normal likelihood ratio, which yields under the implied condition of contiguity the statistics of the detection algorithm under the alternative hypothesis. Thus, optimum detection algorithms in both coherent and incoherent cases are obtained, which are canonical in signal waveform and noise statistics and which have the desired property of asymptotic optimality (acceptably small error probabilities as sample size becomes necessarily large, while the terms in the Taylor expansion of the log-likelihood ratio about the null signal remain fixed). Furthermore, locally optimum detection structures in Gauss-Markov noise are given together with a specific example in the coherent mode of reception in order to demonstrate the significant improvement in performance obtained over independent sampling     

Locally optimum Bayes detection (LOBD) in signal-dependent noise

The locally optimum Bayes detection (LOBD) framework for nonadditive non-Gaussian noise is applied to a particular additive and signal-dependent noise model where the noise components are correlated. Under the proposed observation model, the performance of the LOB detectors is compared with that of well-known conventional receivers     

Weak-Signal DPSK Detection in Narrow-Band Impulsive Noise

The weak-signal receiver for binary differential phase-shift keying (DPSK) in additive noise is derived, and its performance in terms of the error probability in the most general narrow-band impulsive (nonGaussian) noise model, Middleton's class A noise, is analyzed.     

Threshold performance of M-ary noncoherent frequency-shift keying in non-Gaussian noise

An expression for the error probability of M-ary noncoherent frequency-shift keying (NCFSK) for locally optimum threshold detection in non-Gaussian noise, frequently encountered in practice, is derived, which demonstrates that a significant improvement in performance can be achieved when M is greater than two.     

Prion (PrPres) allotypes profiling: a new perspectives from mass spectrometry

Biochemical methods employed for PrPres allotypes profiling are reviewed and compared with the latest mass spectrometric approaches. Emphasis is put on the advantages offered by a recently proposed electrospray strategy.     

Microscopic interacting boson model calculations for even-even <Superscript>128–138</Superscript>Ce nuclei

In this study, we determined the most appropriate Hamiltonian that is needed for the present calculations of energy levels and B(E2) values of ^128–138Ce nuclei which have a mass around A≅130 using the interacting boson model (IBM). Using the best-fitted values of parameters in the Hamiltonian of the IBM-2, we have calculated energy levels and B(E2) values for a number of transitions in ^{128,130,132,134,136,138}Ce. The results were compared with the previous experimental and theoretical (PTSM model) data and it was observed that they are in good agreement. Also some predictions of this model have better accuracy than those of PTSM model. It has turned out that the interacting boson approximation (IBA) is fairly reliable for calculating spectra in the entire set of ^{128,130,132,134,136,138}Ce isotopes and the quality of the fits presented in this paper is acceptable.