Algebraic number theory and code design for Rayleigh fading channels

Algebraic number theory is having an increasing impact in code design for many different coding applications, such as single antenna fading channels and more recently, MIMO systems. Extended work has been done on single antenna fading channels, and algebraic lattice codes have been proven to be an effective tool. The general framework has been settled in the last ten years and many explicit code constructions based on algebraic number theory are now available. The aim of this work is to provide both an overview on algebraic lattice code designs for Rayleigh fading channels, as well as a tutorial introduction to algebraic number theory. The basic facts of this mathematical field will be illustrated by many examples and by the use of a computer algebra freeware in order to make it more accessible to a large audience

Performance of Linear Field Reconstruction Techniques with Noise and Uncertain Sensor Locations

We consider a wireless sensor network, sampling a bandlimited field, described by a limited number of harmonics. Sensor nodes are irregularly deployed over the area of interest or subject to random motion; in addition sensors measurements are affected by noise. Our goal is to obtain a high quality reconstruction of the field, with the mean square error (MSE) of the estimate as performance metric. In particular, we analytically derive the performance of several reconstruction/estimation techniques based on linear filtering. For each technique, we obtain the MSE, as well as its asymptotic expression in the case where the field number of harmonics and the number of sensors grow to infinity, while their ratio is kept constant. Through numerical simulations, we show the validity of the asymptotic analysis, even for a small number of sensors. We provide some novel guidelines for the design of sensor networks when many parameters, such as field bandwidth, number of sensors, reconstruction quality, sensor motion characteristics, and noise level of the measures, have to be traded off

Technical Note: Comparing and ranking soil drought indices performance over Europe, through remote-sensing of vegetation

In the past years there have been many attempts to produce and improve global soil-moisture datasets and drought indices. However, comparing and validating these various datasets is not straightforward. Here, interannual variations in drought indices are compared to interannual changes in vegetation, as captured by NDVI. By comparing the correlations of the different indices with NDVI we evaluated which drought index describes most realistically the actual changes in vegetation. Strong correlation between NDVI and the drought indices were found in areas that are classified as warm temperate climate with hot or warm dry summers. In these areas we ranked the PDSI, PSDI-SC, SPI3, and NSM indices, based on the interannual correlation with NDVI, and found that NSM outperformed the rest. Using this best performing index, and the ICA (Independent Component Analysis) technique, we analyzed the response of vegetation to temperature and soil-moisture stresses over Europe

Reconstruction of Multidimensional Signals from Irregular Noisy Samples

We focus on a multidimensional field with uncorrelated spectrum, and study the quality of the reconstructed signal when the field samples are irregularly spaced and affected by independent and identically distributed noise. More specifically, we apply linear reconstruction techniques and take the mean square error (MSE) of the field estimate as a metric to evaluate the signal reconstruction quality. We find that the MSE analysis could be carried out by using the closed-form expression of the eigenvalue distribution of the matrix representing the sampling system. Unfortunately, such distribution is still unknown. Thus, we first derive a closed-form expression of the distribution moments, and we find that the eigenvalue distribution tends to the Marcenko-Pastur distribution as the field dimension goes to infinity. Finally, by using our approach, we derive a tight approximation to the MSE of the reconstructed field.Comment: To appear on IEEE Transactions on Signal Processing, 200

Algebraic lattice constellations: bounds on performance

In this work, we give a bound on performance of any full-diversity lattice constellation constructed from algebraic number fields. We show that most of the already available constructions are almost optimal in the sense that any further improvement of the minimum product distance would lead to a negligible coding gain. Furthermore, we discuss constructions, minimum product distance, and bounds for full-diversity complex rotated Z[i]/sup n/-lattices for any dimension n, which avoid the need of component interleaving

ESTRUCTURA TRÓFICA DE LA ENTOMOFAUNA ACUÁTICA Y CALIDAD DEL AGUA DE LOS RÍOS ZARATÍ Y LA CHORRERA, PROVINCIA DE COCLÉ, REPÚBLICA DE PANAMÁ

With the aim to determine the water quality and trophic structure of aquatic insect communities in the rivers Zaratí and La Chorrera, a total of three sampling stations were established. Stations were set in a 40 Km transect ensuring the highest amount of habitats for aquatic insects. Stations consisted of different sections ranging from the high, median and lower parts of these rivers. At each sampling station, the sampling effort unit was consistent at one hour. Sampling campaigns were carried out during the month of April to August, 2014. A “D” net (500 μm) was used to scan all habitats within the sampling stations. For the biological water quality analysis the following indexes were employed: Shannon-Weaver and EPT. The assignment of trophic functional groups (collectors-filters, collectors-gatherers, scrapers, predators and Shredders) was done primarily according to the specialized literature on neotropical taxa. For those neotropical taxa with no reference elsewhere, the proposed assignment by Cummins, et al., (2008) was applied. At the Chorrera river, 1434 individuals were collected; these were distributed in seven orders, 28 families and 47 genera. In the Zaratí river, nine orders, 33 families and 49 genera were found among the 1219 collected individuals. The most abundant orders were: Odonata, Hemiptera and Trichoptera. Predators dominated both in abundance and richness at the river assemblage level and transect level in both the Zaratí and La Chorrera rivers. The water quality showed moderate impact. According to our results the best biological index was the EPT (“Taxa”).Con la finalidad de terminar la calidad del agua y la estructura trófica de las comunidades de insectos acuáticos, se establecieron tres estaciones de muestreo a una distancia de 40 km de trayecto a lo largo de los ríos Zaratí y La Chorrera. Las estaciones comprendieron distintos tramos ubicados en las partes alta, media y baja de los ríos. Por cada estación la unidad de esfuerzo de muestreo, fue de una hora y se invirtió el mismo esfuerzo de trabajo por río. El muestreo se realizó desde abril a septiembre de 2014 y se realizó con una red tipo “D” de 500 μm de ojo de malla, mediante arrastres en los hábitats más representativos. Para el análisis de la calidad biológica del agua se emplearon los siguientes índices: Shannon-Wiener y el índice EPT. La asignación de los grupos funcionales alimentarios de colectores-filtradores, colectores-recolectores, raspadores, depredadores y trituradores se hizo primariamente de acuerdo a la literatura especializada para taxones neotropicales y para los que no se encontró información en la literatura para el Neotrópico se utilizó la asignación propuesta por Cummins, et al., (2008) para Norte América. En el río La Chorrera en total se recolectaron 1434 individuos distribuidos en siete órdenes, 28 familias y 47 géneros, y en río Zaratí 1219 individuos distribuidos en nueve órdenes, 33 familias y 49 géneros. Los órdenes más abundantes, en cuanto al número de individuos, en ambos ríos fueron: Odonata, Hemiptera, y Trichoptera. Los depredadores dominaron en riqueza y abundancia a nivel de río y a nivel de tramos en el río La Chorrera y el río Zaratí. La calidad biológica del agua para los ríos la Chorrera y Zaratí fue de moderadamente impactada. El índice biológico que determina mejor la calidad de las aguas es posiblemente el índice EPT (“Taxa”)

ENTOMOFAUNA ACUÁTICA ASOCIADA AL RÍO AGUÉ, EN LA MESA, VERAGUAS, PANAMÁ

This study was carried out in Ague river, La Mesa District, Province of Veraguas. The main purpose of this research was to determine the families and genera of aquatic insects. Six stations were located along the river. These ones were collected twice a month in the morning from Febrary to August 2002. The samples were collected in a period of one hour per station where the capture methods varied in accord to the sustrate. In addition, we used an aquatic net (D-Net) in order to sweep the botton of the river and sumerged marginal vegetation. Besides, the insects located in the muddy-rocky substrate were removed with the help of entomological pincers. As a result, we obtain 81 genera of aquatic insects distributed in 50 families and 10 orders. Hemiptera was the best represented with 22 genera and 10 families. By other insects were distributed as follow: Odonata with 20 genera and 8 families; Coleoptera 13 genera and 12 families; Ephemeroptera with 11 genera and 6 families; Trichoptera 13 genera and 7 families; Diptera with 3 genera and 3 families, while Lepidoptera, Plecoptera, Neuroptera and Blattaria were represented by one genus and one family.El estudio se realizó en el Río Agué, Distrito de La Mesa, Provincia de Veraguas, con el propósito de determinar las familias y géneros de insectos acuáticos existentes. A lo largo del río se ubicaron seis estaciones muestreadas dos veces al mes, en horas de la mañana, desde febrero hasta agosto de 2002; la duración del muestreo fue de una hora, para cada estación. Los métodos de captura variaron de acuerdo al sustrato; se utilizó una red acuática (D-Net) para realizar barridos en el fondo, en la vegetación marginal sumergida, y en el sustrato arenoso, con la ayuda de pinzas entomológicas se desalojaron a los insectos del sustrato fangoso-rocoso. Como resultados, obtuvimos 81 géneros de insectos acuáticos distribuidos en 50 familias y 10 órdenes. El orden mejor representado fue Hemiptera con 22 géneros y 10 familias. Otros órdenes fueron: Odonata con 20 géneros y 8 familias; Coleoptera 13 géneros y 12 familias; Ephemeroptera con 11 géneros y 6 familias; Trichoptera 13 géneros y 7 familias; Diptera con 3 géneros y 3 familias. Lepidoptera, Plecoptera, Neuroptera y Blattaria estuvieron representados por un género y una familia cada uno