Efficient detection algorithms for Multiple-Input Multiple-Output (MIMO) systems

[EN] In the last ten years, one of the most significant technological developments that will lead to the new broadband wireless generation is the communication via Multiple-Input Multiple-Output (MIMO) systems. MIMO systems are known to provide an increase of the maximum rate, reliability and coverage of current wireless communications. Maximum-Likelihood (detection over Gaussian MIMO channels is shown to get the lowest Bit Error Rate for a given scenario. However, it has a prohibitive complexity which grows exponentially with the number of transmit antennas and the size of the constellation. Motivated by this, there is a continuous search for computationally efficient optimal or suboptimal detectors. In this work, we carry out an state of the art review of detection algorithms and propose the combination of a suboptimal MIMO detector called K-Best Sphere Decoder with a channel matrix condition number estimator to obtain a versatile combined detector with predictable performance and suitable for hardware implementation. The effect of the channel matrix condition number in data detection is exploited in order to achieve a decoding complexity lower than the one of already proposed algorithms with similar performance. Some practical algorithms for finding the 2-norm condition number of a given channel matrix and for performing the threshold selection are also presented and their computational costs and accuracy are discussed[ES] Uno de los desarrollos tecnol'ogicos m'as significativos de la ' ultima d'ecada que llevar'an a la nueva generaci'on de banda ancha en movilidad es la comunicaci'on mediante sistemas de m' ultiples entradas y m' ultiples salidas (MIMO). Los sistemas MIMO proporcionan un notable incremento en la capacidad, fiabilidad y cobertura de las comunicaciones inal'ambricas actuales. Se puede demostrar que la detecci'on 'optima o dem'axima verosimilitud (ML) en canales MIMO Gaussianos proporciona la m'¿nima tasa de error de bit (BER) para un escenario dado pero tiene el inconveniente de que su complejidad crece exponencialmente con el n'umero de antenas y el tama¿no de la constelaci'on utilizada. Por este motivo, hay una cont'¿nua b' usqueda de detectores 'optimos o sub'optimos que sean m'as eficientes computacionalmente. En este trabajo, se ha llevado a cabo una revisi 'on del estado del arte de los principales algoritmos de detecci'on para sistemas MIMO y se ha propuesto la combinaci'on de un detector MIMO sub'optimo conocido como K-Best Sphere Decoder con un estimador del n'umero de condici'on de la matriz de canal, para conseguir un detector combinado basado en umbral con complejidad predecible y adecuado para implementaci'on en hardware. Se ha explotado el efecto del n'umero de condici'on en la detecci'on de datos para disminuir la complejidad de los algoritmos de detecci 'on existentes sin apenas alterar sus prestaciones. Por ' ultimo tambi'en se presentan distintos algoritmos pr'acticos para encontrar el dos n'umero de condici'on as'¿ como para realizar la selecci 'on del umbral.Roger Varea, S. (2008). Efficient detection algorithms for Multiple-Input Multiple-Output (MIMO) systems. http://hdl.handle.net/10251/12200Archivo delegad

Design and Implementation of Efficient Algorithms for Wireless MIMO Communication Systems

En la última década, uno de los avances tecnológicos más importantes que han hecho culminar la nueva generación de banda ancha inalámbrica es la comunicación mediante sistemas de múltiples entradas y múltiples salidas (MIMO). Las tecnologías MIMO han sido adoptadas por muchos estándares inalámbricos tales como LTE, WiMAS y WLAN. Esto se debe principalmente a su capacidad de aumentar la máxima velocidad de transmisión , junto con la fiabilidad alcanzada y la cobertura de las comunicaciones inalámbricas actuales sin la necesidad de ancho de banda extra ni de potencia de transmisión adicional. Sin embargo, las ventajas proporcionadas por los sistemas MIMO se producen a expensas de un aumento sustancial del coste de implementación de múltiples antenas y de la complejidad del receptor, la cual tiene un gran impacto sobre el consumo de energía. Por esta razón, el diseño de receptores de baja complejidad es un tema importante que se abordará a lo largo de esta tesis. En primer lugar, se investiga el uso de técnicas de preprocesado de la matriz de canal MIMO bien para disminuir el coste computacional de decodificadores óptimos o bien para mejorar las prestaciones de detectores subóptimos lineales, SIC o de búsqueda en árbol. Se presenta una descripción detallada de dos técnicas de preprocesado ampliamente utilizadas: el método de Lenstra, Lenstra, Lovasz (LLL) para lattice reduction (LR) y el algorimo VBLAST ZF-DFE. Tanto la complejidad como las prestaciones de ambos métodos se han evaluado y comparado entre sí. Además, se propone una implementación de bajo coste del algoritmo VBLAST ZF-DFE, la cual se incluye en la evaluación. En segundo lugar, se ha desarrollado un detector MIMO basado en búsqueda en árbol de baja complejidad, denominado detector K-Best de amplitud variable (VB K-Best). La idea principal de este método es aprovechar el impacto del número de condición de la matriz de canal sobre la detección de datos con el fin de disminuir la complejidad de los sistemasRoger Varea, S. (2012). Design and Implementation of Efficient Algorithms for Wireless MIMO Communication Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16562Palanci

Identifying longitudinal sustainable hierarchies in activities of daily living

© 2017 Elsevier B.V. Activities of daily living serve as an indicator of progression in disability and rehabilitation. It is know that some of the measurement scales used show hierarchical properties indicating that activities of daily living are lost and gained in a consistent pattern. Few studies have investigated the extent to which these patterns are sustained across time and across a range of disability. The study aimed to investigate the hierarchical properties of the activity of daily living items in the ValGraf functional ability scale, to establish if there is a hierarchy of items in the scale and to study the sustainability of the hierarchy over time. Secondary analysis of a retrospective database from 13,113 people over 65 years in 105 nursing homes in northern Italy, between 2008 and 2013 was conducted. Data were gathered 6-monthly and analysed using Mokken scaling to identify a hierarchy of items in the scale and if this was sustainable over time. A sustainable hierarchy of items was observed running in difficulty from urinary incontinence to feeding. The hierarchical structure of the activities of daily living observed in the present study is stable over time meaning that changes in total score for these items can be compared meaningfully across time

It depends what you do in the laboratory

Let us start by stating a strong opinion: psychology can only claim honesty when it makes the effort to relate its own theories and other observations about human behaviour and experience to actual human behaviour and experience in the real world. In this respect, we agree with some of the assumptions the authors make in this article and we share with the authors a sense of frustration that so much effort in cognitive psychology can sometimes yield very little insight beyond the relative sterility shown by some laboratory phenomena

Some robust higher-level percepts for music

We explored a range of higher-level percepts in music. Participants were asked to make two-alternative forced-choice judgments of extracts of instrumental music on various dipole categories, such as happy/sad or male/female. The consistency with which each stimulus was judged on a response category across listeners provides an indication of the extent to which the musical percept can be mapped reliably onto that dimension. High consistency would suggest that the response category is related to one of the natural perceptual dimensions for music. We found very high consistency (90% +) for various response categories normally used as descriptions of people (such as male/female and happy/sad). Other types of response category gave much lower consistency. Perhaps our participants are experts in making fine distinctions in person-related categories for almost any stimulus. We tested this with a control experiment where foodstuffs replaced the musical stimuli. We did not find high agreement for person-related categories. The differences between responses to music and food were statistically highly significant

Analysis of local and global timing and pitch change in ordinary melodies

This paper describes a set of statistical relationships between pitch change structure and timing structures in ordinary melodies. We obtained over 5000 MIDI files for ordinary western melodies, each with a prescribed tempo, so that note timings could be given in seconds. 1): We find that the frequencies of occurrence of different pitch change sizes are stationary: they do not vary during the time-course of a melody, apart from during the first 1 second and the final 1 second. 2): There is an inverse relationship between the mean (absolute) pitch change size in a melody and the mean time interval between successive note onsets: melodies with larger pitch changes tend to be faster.3): The time intervals between successive occurrences of the same pitch change size reflect an active process. 4): For each melody, we construct a function showing the temporal rise and fall in the likelihood of the melody as given by the log of the reciprocal of the frequency of the most recent pitch change. Fourier analysis of these functions shows a regular pattern of coherent variability with a period of between 2 and 6 seconds. Low likelihood portions of a melody are balanced by higher likelihood ones over a time scale of a few seconds

The perception of local and global timing in simple melodies

Local relations refer to adjacent events (such as the time between successive notes in amelody); global relations refer to a continuous succession of local events (such as the rhythmic timing of the complete series of notes in a melody). Tones in a short auditory sequence can have their perceived timing distorted by local pitch relations. The Tau and Kappa timing effects in visual motion stimuli have equivalent auditory pitch motion versions (Shigeno 1993) where the perceived delay from one tone to the next depends on local pitch separation. We report data which show local distortions in the perceived duration of a sequence of 3 tones where the first and last tones have one pitch and the middle tone another pitch. Perceived duration increases with the pitch interval between the middle tone and the others: the larger the pitch interval the longer the perceived duration. We report a range of results which allow us to relate this finding to the relative frequency of the melodic intervals in “vernacular” western tonal music: melodic events that are uncommon (such as a pitch change of a major 7th) are perceived to last longer than identically timed common ones (such as major 2nd). This local effect suggests that there should be an equivalent global effect: large intervals should tend to make melodies sound slower. However, we also report data showing that melodies with frequent large intervals tend to have their perceptual characteristics (such as happiness/sadness) judged as if the melody is faster (not slower) than melodies without large intervals. This shows a discrepancy between local timing and global timing. This set of findings is difficult to reconcile with any unitary additive model of time perception. We will describe an alternative account of time based on the nature of events. Uncommon events happen less frequently (by definition) and therefore the time between uncommon events will normally be longer that the time between common events. In this sense, uncommon events can be said to dilate the perception of time. When events happen more frequently than usual, a melody sounds rushed

Different roles for non-receptor tyrosine kinases in arachidonate release induced by zymosan and Staphylococcus aureus in macrophages

BACKGROUND: Yeast and bacteria elicit arachidonate release in macrophages, leading to the formation of leukotrienes and prostaglandins, important mediators of inflammation. Receptors recognising various microbes have been identified, but the signalling pathways are not entirely understood. Cytosolic phospholipase A(2 )is a major down-stream target and this enzyme is regulated by both phosphorylation and an increase in intracellular Ca(2+). Potential signal components are MAP kinases, phosphatidylinositol 3-kinase and phospholipase Cγ2. The latter can undergo tyrosine phosphorylation, and Src family kinases might carry out this phosphorylation. Btk, a Tec family kinase, could also be important. Our aim was to further elucidate the role of Src family kinases and Btk. METHODS: Arachidonate release from murine peritoneal macrophages was measured by prior radiolabeling. Furthermore, immunoprecipitation and Western blotting were used to monitor changes in activity/phosphorylation of intermediate signal components. To determine the role of Src family kinases two different inhibitors with broad specificity (PP2 and the Src kinase inhibitor 1, SKI-1) were used as well as the Btk inhibitor LFM-A13. RESULTS: Arachidonate release initiated by either Staphylococcus aureus or yeast-derived zymosan beads was shown to depend on members of the Src kinase family as well as Btk. Src kinases were found to act upstream of Btk, phosphatidylinositol 3-kinase, phospholipase Cγ2 and the MAP kinases ERK and p38, thereby affecting all branches of the signalling investigated. In contrast, Btk was not involved in the activation of the MAP-kinases. Since the cytosolic phospholipase A(2 )in macrophages is regulated by both phosphorylation (via ERK and p38) and an increase in intracellular Ca(2+), we propose that members of the Src kinase family are involved in both types of regulation, while the role of Btk may be restricted to the latter type. CONCLUSION: Arachidonate release induced by either Staphylococcus aureus or zymosan was found to depend on Src family kinases as well as Btk. While members of the Src kinase family were shown to act upstream of Btk and the MAP kinases, Btk plays another role independent of MAP kinases, but down-stream of the Src family kinases

Konstruktive Fallbesprechungen im Mentoring: Erfahrungen aus einem Versuch im Rahmen der berufspraktischen Ausbildung

This article describes an attempt to optimize teacher mentoring during pre-service training at schools through constructive casework. Initially the requirements and characteristics of constructive casework are discussed. Then the theoretical foundations for the key elements are developed. In addition, the systematic contribution of casework to competency development, and the implications for cooperation in mentoring are addressed. One focus is on the conditions of the experiment, whereby sequences of conversation protocols with a student are analyzed. The example shows that constructive casework can make an important contribution to competency development, which generalizes beyond the specific requirements of the particular situation.Der Beitrag gibt Einblick in einen Versuch, Mentoring im Praktikum durch konstruktive Fallarbeit zu optimieren. Zu Beginn werden Erfordernisse und Charakteristika konstruktiver Fallarbeit behandelt. Anschliessend werden die Eckpunkte des Versuchs theoretisch untermauert. Erläutert wird, was unter konstruktiver Fallarbeit verstanden wird. Im Weiteren werden ihr Beitrag zum systematischen Kompetenzaufbau und ihre Konsequenzen für die Kooperation im Mentoring angesprochen. Einen Schwerpunkt bilden die Rahmenbedingungen des durchgeführten Versuchs, der anhand von Sequenzen aus Gesprächsprotokollen mit einer Studentin konkretisiert wird. Das Beispiel zeigt, dass konstruktive Fallarbeit im Praktikum einen wichtigen Beitrag zum Kompetenzaufbau leisten kann, der über die Bewältigung der spezifischen Situation hinausgeht