Эмпирический подход к оценке помехоустойчивости сигналов фазовой модуляции

Высокая спектральная эффективность сигналов с непрерывной фазовой модуляцией определила их известность и активное применение в различных радиотехнических проектах. Уникальность свойств таких сигналов связана с сохранением непрерывности их фазы при смене информационных посылок на длительности символа. Вместе с тем до недавнего времени из всего широкого класса сигналов с непрерывной фазовой модуляцией наибольшее распространение получили различные вариации так называемых сигналов частотной модуляцией с минимальным сдвигом. Однако это далеко не единственные представители класса сигналов с непрерывной фазовой модуляцией, обладающие свойством высокой спектральной компактности. Исследованы не менее интересные сигналы этого класса, формируемые посредством двойной фазовой модуляции. Представлены аналитические выражения их синтеза, обоснована их принадлежность к классу сигналов с непрерывной фазовой модуляцией. Также исследованы временные свойства фазовой функции, рекомендованной МСЭ-R SM.328-11 для синтеза сигналов с непрерывной фазовой модуляцией, приведены временные и частотные фрагменты сигналов с минимальным сдвигом в сравнении сигналами с двоичной фазовой манипуляцией. Представлены этапы аналитического вывода модели помехоустойчивости сигналов с непрерывной фазовой модуляцией по показателю вероятности битовой ошибки на основе эмпирического подхода. Показана общность полученной модели с известным выражением для сигналов с минимальным сдвигом путем исследования разностной функции ошибки аппроксимации (ошибка порядка 10-3), что позволило получить более компактное представление разработанной модели применительно к сигналам с двойной фазовой модуляцией. Доказано, что такие сигналы обладают более высокими свойствами помехоустойчивости по отношению к сигналам с минимальным сдвигом (порядка 0,5 дБ по уровню ошибки 10-5). Указанный результат получен на основе исследования функций различия, определяемых разностью между сигнальными символами соответствующих информационным значениям «1» и «0». Определены направления дальнейшего исследования

Эмпирический подход к оценке помехоустойчивости сигналов фазовой модуляции

The high spectral efficiency of signals with continuous phase modulation (CPM) has determined their popularity and active use in various radio engineering projects. The uniqueness of the properties of CPM signals is associated with the preservation of the continuity of their phase when changing information messages for the duration of a symbol. At the same time, until recently, of the entire wide class of signals with continuous phase modulation, the most widespread were various variations, the so-called Minimum Shift Keying (MSK) signals. However, these are far from the only representatives of the class of CPM signals with the property of high spectral compactness. This article examines no less interesting signals of this class, formed by means of Dual Phase Modulation (DPM). In particular, analytical expressions of their synthesis are presented, their belonging to the class of CPM signals is substantiated. In addition, the article investigates the temporal properties of the phase function recommended by ITU-R SM.328-11 for the synthesis of signals with continuous phase modulation, presents the time and frequency fragments of MSK signals in comparison with signals with Binary Phase Shift Keying (BPSK). The stages of the analytical derivation of the model of noise immunity of PCM signals in terms of the probability of a bit error based on an empirical approach are presented. The generality of the obtained model with the known expression for MSK signals is shown by studying the difference function of the approximation error (error of the order of 10-3), which made it possible to obtain a more compact representation of the developed model in relation to DPM signals. It has been proven that DPM signals have higher noise immunity properties in relation to MSK signals (about 0.5 dB at an error level of 10-5), using the results of studying the difference functions determined by the difference between the signal symbols corresponding to the information values "1" and "0". The directions of further research are determined.Высокая спектральная эффективность сигналов с непрерывной фазовой модуляцией определила их известность и активное применение в различных радиотехнических проектах. Уникальность свойств таких сигналов связана с сохранением непрерывности их фазы при смене информационных посылок на длительности символа. Вместе с тем до недавнего времени из всего широкого класса сигналов с непрерывной фазовой модуляцией наибольшее распространение получили различные вариации так называемых сигналов частотной модуляцией с минимальным сдвигом. Однако это далеко не единственные представители класса сигналов с непрерывной фазовой модуляцией, обладающие свойством высокой спектральной компактности. Исследованы не менее интересные сигналы этого класса, формируемые посредством двойной фазовой модуляции. Представлены аналитические выражения их синтеза, обоснована их принадлежность к классу сигналов с непрерывной фазовой модуляцией. Также исследованы временные свойства фазовой функции, рекомендованной МСЭ-R SM.328-11 для синтеза сигналов с непрерывной фазовой модуляцией, приведены временные и частотные фрагменты сигналов с минимальным сдвигом в сравнении сигналами с двоичной фазовой манипуляцией. Представлены этапы аналитического вывода модели помехоустойчивости сигналов с непрерывной фазовой модуляцией по показателю вероятности битовой ошибки на основе эмпирического подхода. Показана общность полученной модели с известным выражением для сигналов с минимальным сдвигом путем исследования разностной функции ошибки аппроксимации (ошибка порядка 10-3), что позволило получить более компактное представление разработанной модели применительно к сигналам с двойной фазовой модуляцией. Доказано, что такие сигналы обладают более высокими свойствами помехоустойчивости по отношению к сигналам с минимальным сдвигом (порядка 0,5 дБ по уровню ошибки 10-5). Указанный результат получен на основе исследования функций различия, определяемых разностью между сигнальными символами соответствующих информационным значениям «1» и «0». Определены направления дальнейшего исследования

Proceedings of the Mobile Satellite Conference

A satellite-based mobile communications system provides voice and data communications to mobile users over a vast geographic area. The technical and service characteristics of mobile satellite systems (MSSs) are presented and form an in-depth view of the current MSS status at the system and subsystem levels. Major emphasis is placed on developments, current and future, in the following critical MSS technology areas: vehicle antennas, networking, modulation and coding, speech compression, channel characterization, space segment technology and MSS experiments. Also, the mobile satellite communications needs of government agencies are addressed, as is the MSS potential to fulfill them

Mathematical Biology

Mathematical biology is a fast growing field of research, which on one hand side faces challenges resulting from the enormous amount of data provided by experimentalists in the recent years, on the other hand new mathematical methods may have to be developed to meet the demand for explanation and prediction on how specific biological systems function

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Formulation and Assessment of Taste-masked Electrospun Fibre Mats for Paediatric Drug Delivery

Since the Paediatric Regulation came into force by the European Medicines Agency in 2007, the drive to formulate age-appropriate dosage forms has been accelerated. The aim of this thesis was to develop new approaches for paediatric formulation design through the optimisation of novel taste-masking and taste-assessment methods. Electrospinning was demonstrated to be a suitable taste-masking technology, producing fibre mats that can be further formulated into easy to swallow oral films. The electrospinning of Eudragit E PO, a taste-masking polymer, was optimised using Quality by Design principles and in particular Design of Experiment. To further enhance the taste-masking capability of the electrospun mat, co-axial electrospinning was utilised using another taste-masking polymer, Kollicoat Smartseal. The use of both polymers successfully taste-masked chlorpheniramine maleate, a known bitter anti-histamine. This was demonstrated using an electronic biosensor tasting system or E-tongue. The E-tongue was used to assess the bitterness threshold of this model drug but also of other standard bitter drugs for benchmarking. In addition, it was used to taste-assess various formulations which aided in ranking and deselecting formulations. Electrospun fibre mats can be further processed into a number of different dosage forms for final presentation to the patient. The fibre mats were designed to be presented as an oral film. A water-soluble outer layer was added to the films using multi-axial electrospinning. A human panel was conducted to investigate the mouthfeel and overall acceptability of electrospun PVA films versus solvent-cast PVA films. The electrospun films were found to be as acceptable as the standard solvent-cast films, a very promising result for clinical translation. PVA and PVP were electrospun with the previously optimised polymers using tri-axial and tetra-axial electrospinning. The taste of the multi-axial electrospun fibre mats were assessed and it was found that adding a water-soluble outer layer reduces the taste-masking ability. Thus, it was found that electrospinning of a bitter drug using hydrophobic taste-masking polymers is very promising in the formulation of paediatric oral films

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Development and application of an economic approach to isotope labeling in higher eukaryotes for NMR studies

Cutting-edge structural studies by crystallography are presently aimed at very complex targets including membrane, multi-domain and secreted proteins of human origin. Such proteins can often only be expressed in higher eukaryotic systems, such as insect or mammalian cell lines due to the requirement of the complex eukaryotic protein expression and post-translational modification machinery. For NMR studies, the need of isotope labeling poses extreme challenges in such eukaryotic hosts, since the growth media need to contain isotope-labeled amino acids. The costs of commercially available isotope-labeled amino acids are very high and so far even prohibitive in the case of deuteration. This thesis describes the development of an economic approach to isotope labeling in higher eukaryotes, where the necessary labeled amino acids are provided to the growth media from autolyzed yeast grown on inexpensive 13C glucose, 15N ammonium salt and 2H2O. The method was used in the baculovirus-infected insect cell system to produce isotope-labeled proteins relevant to human health and their study by NMR. Chapter 1 provides an introduction to recombinant expression in insect cell lines and the use of the baculovirus expression vector system. Furthermore, the amino acid metabolism in insect cells and its relevance for isotope labeling is discussed. Frequently used approaches to isotope labeling and their applications are outlined. Chapter 2 describes in detail the production of isotope-labeled yeast extracts and their supplementation to insect cell growth media for labeled protein expression. Parts of this chapter have been published (Opitz et al., An economic approach to efficient isotope labeling in insect cells using homemade 15N-, 13C- and 2H-labeled yeast extracts. J. Biomol. NMR, 2015). The method achieves uniform protein 15N and 13C labeling of up to 90 % and deuteration levels of >60 %, which are the highest reported incorporation levels based on cellular extracts so far. Chapter 3 describes the design of a thermostabilized mutant of the turkey β1-adrenergic receptor (TS-β1AR) for NMR solution studies. This mutant was expressed with selective 15N-valine labeling in insect cells and used for an extensive NMR characterization of ligand interactions. It was possible to follow ligand-induced backbone motions at many key residues in the receptor. The latter results have been published (Isogai, Deupi, Opitz et al., Backbone NMR reveals allosteric signal transduction networks in the β1-adrenergic receptor. Nature, 2016). The final section of the chapter shows the expression of uniformly 2H-15N labeled TS-β1AR, which has been used to record high-quality 15N-edited NOESY spectra and obtain a number of further backbone resonance assignments. Chapter 4 describes the expression of the human lipopolysaccharide-binding protein (hLBP) for NMR studies in baculovirus-infected insect cells by secretion of the protein to the culture medium. A labeling scheme was explored based on the combination of isotope-labeled autolyzed yeast and commercial extracts of algal cells. The combined approach made it possible to produce milligram quantities of uniformly 15N-labeled hLBP and to acquire two-dimensional 1H-15N-TROSY spectra. Chapter 5 describes the enzymatic synthesis of 15N2-L-glutamine from inexpensive 2-oxoglutaric acid and 15N ammonium salt. Since supplementation of L-glutamine is required for efficient expression, the method further reduces the costs of the labeling approach based on autolyzed yeast and enables economic production of selectively deuterated L-glutamine. For additional cost reduction, also the recombinant expression of glutamate-ammonia ligase was established. Chapter 6 describes the use of autolyzed yeast as an economical source of labeled amino acids in the cell-free expression system. An initial protocol for high-yield expression was established and its optimization is discussed. Isotope labeling by 15N and 2H is demonstrated for the green fluorescent protein GFP produced in the cell-free expression system based on isotope-labeled yeast. Chapter 7 describes a proteomics approach to study short-term adaptation of E. coli to growth on 2H7-glucose and 2H2O. Characterization of the cellular adaptation process has implications for the production of deuterated proteins. The results show that deuterated media induce differential expression of proteins involved in the response to osmotic and temperature-induced stress. The data further indicate downregulation of proteins involved in ribosome biogenesis and differential activation of chaperones targeting nucleic acids as well as proteins. Simultaneously, an alteration of the energy metabolism was observed in the perdeuterated environment, in particular upregulation of anaplerotic reactions in the TCA cycle. Chapter 8 explores the use of isotope-labeled yeast as an economic source of amino acids for labeling in mammalian cells. The initial results indicate that, similar to the protocol applied in insect cells, inexpensive dropout media supplemented by labeled yeast extracts enable good expression of the uniformly labeled angiotensin II receptor type 1a for NMR studies