378 research outputs found
Transmitter-side antennas correlation in SVD-assisted MIMO systems
MIMO techniques allow increasing wireless channel performance by decreasing the BER and increasing the channel throughput and in consequence are included in current mobile communication standards. MIMO techniques are based on benefiting the existence of multipath in wireless communications and the application of appropriate signal processing techniques. The singular value decomposition (SVD) is a popular signal processing technique which, based on the perfect channel state information (PCSI) knowledge at both the transmitter and receiver sides, removes inter-antenna interferences and improves channel performance. Nevertheless, the proximity of the multiple antennas at each front-end produces the so called antennas correlation effect due to the similarity of the various physical paths. In consequence, antennas correlation drops the MIMO channel performance. This investigation focuses on the analysis of a MIMO channel under transmitter-side antennas correlation conditions. First, antennas correlation is analyzed and characterized by the correlation coefficients. The analysis describes the relation between antennas correlation and the appearance of predominant layers which significantly affect the channel performance. Then, based on the SVD, pre- and post-processing is applied to remove inter-antenna interferences. Finally, bit- and power allocation strategies are applied to reach the best performance. The resulting BER reveals that antennas correlation effect diminishes the channel performance and that not necessarily all MIMO layers must be activated to obtain the best performance
Discrete wavelet transform de-noising in eukaryotic gene splicing
<p>Abstract</p> <p>Background</p> <p>This paper compares the most common digital signal processing methods of exon prediction in eukaryotes, and also proposes a technique for noise suppression in exon prediction. The specimen used here which has relevance in medical research, has been taken from the public genomic database - GenBank.</p> <p>Methods</p> <p>Here exon prediction has been done using the digital signal processing methods viz. binary method, EIIP (electron-ion interaction psuedopotential) method and filter methods. Under filter method two filter designs, and two approaches using these two designs have been tried. The discrete wavelet transform has been used for de-noising of the exon plots.</p> <p>Results</p> <p>Results of exon prediction based on the methods mentioned above, which give values closest to the ones found in the NCBI database are given here. The exon plot de-noised using discrete wavelet transform is also given.</p> <p>Conclusion</p> <p>Alterations to the proven methods as done by the authors, improves performance of exon prediction algorithms. Also it has been proven that the discrete wavelet transform is an effective tool for de-noising which can be used with exon prediction algorithms.</p
Decentralized Estimation over Orthogonal Multiple-access Fading Channels in Wireless Sensor Networks - Optimal and Suboptimal Estimators
Optimal and suboptimal decentralized estimators in wireless sensor networks
(WSNs) over orthogonal multiple-access fading channels are studied in this
paper. Considering multiple-bit quantization before digital transmission, we
develop maximum likelihood estimators (MLEs) with both known and unknown
channel state information (CSI). When training symbols are available, we derive
a MLE that is a special case of the MLE with unknown CSI. It implicitly uses
the training symbols to estimate the channel coefficients and exploits the
estimated CSI in an optimal way. To reduce the computational complexity, we
propose suboptimal estimators. These estimators exploit both signal and data
level redundant information to improve the estimation performance. The proposed
MLEs reduce to traditional fusion based or diversity based estimators when
communications or observations are perfect. By introducing a general message
function, the proposed estimators can be applied when various analog or digital
transmission schemes are used. The simulations show that the estimators using
digital communications with multiple-bit quantization outperform the estimator
using analog-and-forwarding transmission in fading channels. When considering
the total bandwidth and energy constraints, the MLE using multiple-bit
quantization is superior to that using binary quantization at medium and high
observation signal-to-noise ratio levels
Performance analysis of MIMO-SESS with Alamouti scheme over Rayleigh fading channels
Las unidades fraseológicas han estado presentes en los repertorios desde los comienzos
de la lexicografÃa. Y no solamente en los diccionarios generales, sino también en las
catalogaciones especializadas, tanto de naturaleza monolingüe como bilingüe. No
obstante, siempre ha existido dificultad terminológica para la categorización de los
diferentes fenómenos del discurso repetido. Si bien esto no ha sido un inconveniente
para que se hayan publicado numerosas compilaciones, sobre todo de refranes en un
principio, ya que en la actualidad, fundamentalmente, gracias al auge de los estudios
teóricos sobre fraseologÃa, han proliferado otras obras (algunas aplicadas a la
glosodidáctica, dada su importancia hoy en dÃa) en las que se da cabida con mayor
frecuencia a enunciados de valor especÃfico y a locuciones; en unas ocasiones,
ahondando en el origen que les dio entidad y, en otras, estableciendo etiquetados
precisos que hasta el momento solÃan estar ausentes, pero con la finalidad, al fin y al
cabo, de desentrañar el sentido, dada la escasa deducibilidad que presentan estas
secuencias fijadas por la simple suma de sus elementos constitutivos. Un análisis de
estos repertorios a través de los siglos, es, por tanto, el objetivo de este trabajo.Since the beginning of lexicography, phraseological units have been included in
repertoires; not only in general dictionaries, but also in monolingual and bilingual
specialized catalogues. However, there have always been terminological difficulties for
classifying various phenomena of repeated speech. Although this has not been
inconvenient for publishing many compilations of sayings, especially at the beginning,
because nowadays they frequently include utterances with precise value and idioms,
mainly due to the rise of theoretical studies on phraseology (some applied to ASL
Linguistics, given its importance today). In them, sometimes, the origin of the
phraseological unit is included and, in others, accurate labels that were absent before are
determined in order, finally and ultimately, to unravel the meaning, given the reduced
deductibility that these sequences present from the simple sum of their constituent
elements. The objective of this work is, therefore, an analysis of these repertories
throughout the centuries
Adaptive Models for Gene Networks
Biological systems are often treated as time-invariant by computational models that use fixed parameter values. In this study, we demonstrate that the behavior of the p53-MDM2 gene network in individual cells can be tracked using adaptive filtering algorithms and the resulting time-variant models can approximate experimental measurements more accurately than time-invariant models. Adaptive models with time-variant parameters can help reduce modeling complexity and can more realistically represent biological systems
Power allocation strategies for distributed precoded multicell based systems
Multicell cooperation is a promising solution for cellular wireless systems to mitigate intercell interference, improve system fairness, and increase capacity. In this article, we propose power allocation techniques for the downlink of distributed, precoded, multicell cellular-based systems. The precoder is designed in two phases: first the intercell interference is removed by applying a set of distributed precoding vectors; then the system is further optimized through power allocation. Three centralized power allocation algorithms with per-BS power constraint and diferente complexity trade-offs are proposed: one optimal in terms of minimization of the instantaneous average bit error rate (BER), and two suboptimal. In this latter approach, the powers are computed in two phases. First, the powers are derived under total power constraint (TPC) and two criterions are considered, namely, minimization of the instantaneous average BER and minimization of the sum of inverse of signal-to-noise ratio. Then, the final powers are computed to satisfy the individual per-BS power constraint. The performance of the proposed schemes is evaluated, considering typical pedestrian scenarios based on LTE specifications. The numerical results show that the proposed suboptimal schemes achieve a performance very close to the optimal but with lower computational complexity. Moreover, the performance of the proposed per-BS precoding schemes is close to the one obtained considering TPC over a supercell.Portuguese CADWIN - PTDC/ EEA TEL/099241/200
Differential spatial modulation for high-rate transmission systems
This paper introduces a new differential spatial modulation (DSM) scheme which subsumes both the previously introduced DSM and high-rate spatial modulation (HR-SM) for wireless multiple input multiple output (MIMO) transmission. By combining the codeword design method of the HR-SM scheme with the encoding method of the DSM scheme, we develop a high-rate differential spatial modulation (HR-DSM) scheme equipped with an arbitrary number of transmit antennas that requires channel state information (CSI) neither at the transmitter nor at the receiver. The proposed approach can be applied to any equal energy signal constellations. The bit error rate (BER) performance of the proposed HR-DSM schemes is evaluated by using both theoretical upper bound and computer simulations. It is shown that for the same spectral efficiency and antenna configuration, the proposed HR-DSM outperforms the DSM in terms of bit error rate (BER) performance
Graphite Epoxy Defect Classification of Ultrasonic Signatures Using Statistical and Neural Network Techniques
The use of graphite epoxy composite materials in thick sections for structural applications in naval vessels is achieving worldwide interest [1]. Current and future applications of composites include construction of hulls, superstructures, weight critical articles, secondary structures and quasi-structural components.</p
- …