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

Recent Trends in Communication Networks

In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges

Entwicklung einer berührungslosen EEG-Mütze mittels kapazitiver Elektroden

Non-contact capacitive electrodes for bioelectric diagnostics provide an interesting alternative to classical galvanically coupled electrodes. Such a low cost diagnostic system can be applied without preparation time and in mobile wireless environments. For even higher user comfort textile capacitive electrodes are preferable. In this work, a comprehensive model for the electronic noise properties and frequency dependent responses of PCB-based, as well as textile non-contact capacitive electrodes, is presented. A thorough study of the influence of the electrical components on the resulting noise properties of these electrodes, is provided by independently measuring the corresponding noise spectra. The most important low frequency noise source of capacitive electrode is the necessary high input bias resistance. By comparing the noise measurements with the theoretical noise model of the electrode, it is concluded that the surface of the electrode contributes to an additional 1/f-power noise. It is also found that the highest possible coupling capacitance is most favorable for low noise behavior. Therefore, we implemented electrodes with electrically conducting fabric surfaces. With these electrodes, it is possible to enlarge the surface of the electrode while simultaneously maintaining a small distance between the body and the electrode over the whole surface area, thus maximizing the capacitance. We also show that the use of textile capacitive electrodes, reduces the noise considerably. Furthermore, this thesis describes the construction of a capacitive non-contact textile electroencephalography measuring hat (cEEG hat) with seven measuring channels. This hat benefits from the low noise characteristics of the integrated developed textile capacitive electrodes. The measured noise spectrum of this cEEG hat shows low noise characteristics at low frequencies. This fulfills many requirements for measuring brain signals. The implemented cEEG hat is comfortable to wear during very long measurements and even during sleep periods. In contrast to common methods, the cEEG hat provides a possibility of measuring EEG signal during sleep outside laboratories and in the comfort of home. EEG sleep measurements shown in this work, are recorded inside a normal apartment. The possibility of brain computer interface application is also shown by measuring steady state visually evoked potentials (SSVEP) at different frequencies.Berührungslose, kapazitive Elektroden für bioelekrische Untersuchungen stellen eine interessante Alternative zu klassischen galvanisch gekoppelten Elektroden dar. Ein solches preisgünstiges Diagnosesystem kann ohne lange Vorbereitungszeit und in mobilen Umgebungen eingesetzt werden. Für gesteigerten Tragekomfort sind textile Elektroden von Vorteil. In dieser Arbeit wird eine umfassende Beschreibung der elektronischen Rauscheigenschaften und des frequenzabhängigen Verhaltens von sowohl platinenbasierten, als auch textilen kapazitiven Elektroden vorgestellt. Die Einflüsse aller elektronischen Komponenten auf die resultierenden Rauscheigenschaften werden durch Messungen der entsprechenden Rauschspektren untersucht. Die wichtigste niederfrequente Rauschquelle kapazitiver Elektroden stellt der notwendige und zugleich hohe Bias-Eingangswiderstand dar. Durch Vergleich der gemessenen Rauschspektren mit dem theoretischen Modell wird die Oberfläche der Elektroden als eine zusätzliche 1/f-Rauschquelle identifiziert. Dabei ist die größtmögliche Kopplungskapazität vorteilhaft für ein niedriges Rauschen. Deshalb setzen wir im Folgenden Elektroden aus elektrisch leitfähigen Textilien ein. Mit diesen Elektroden ist es möglich, die Oberfläche der Elektrode unter gleichzeitiger Beibehaltung eines kleinen Abstandes zum Körper zu vergrößern. Dies maximiert wiederum die Kapazität. Wir zeigen zudem, dass die Verwendung textiler kapazitiver Elektroden die Rauscheigenschaften deutlich verbessert. Desweiteren wird in dieser Arbeit die Konstruktion eines kapazitiven, berührungslosen EEG-Helmes (cEEG-Mütze) mit sieben Kanälen beschrieben. Dieser Helm profitiert von den guten Rauscheigenschaften der zuvor entwickelten und hier integrierten textilen Elektroden. Die gemessenen Rauschspektren zeigen ein niedriges Rauschen im unteren Frequenzbereich. Dies erfüllt viele Voraussetzungen für die Messung von Gehirnsignalen. Die erstellte cEEG-Mütze lässt sich während langer Messzeiten und Schlafperioden angenehm tragen. Im Gegensatz zu herkömmlichen Methoden ermöglicht sie Messungen außerhalb von Laboratorien und im gewohnten Umfeld. Alle in dieser Arbeit gezeigten Schlafmessungen wurden in einer normalen Wohnung aufgezeichnet. Außerdem wird die Einsatzmöglichkeit für sogenannte ”Gehirn-Computer-Schnittstellen” anhand der Messung von ”steady state visually evoked potentials” (SSVEP) Signalen bei verschiedenen Frequenzen demonstriert

High Performance Optical Transmitter Ffr Next Generation Supercomputing and Data Communication

High speed optical interconnects consuming low power at affordable prices are always a major area of research focus. For the backbone network infrastructure, the need for more bandwidth driven by streaming video and other data intensive applications such as cloud computing has been steadily pushing the link speed to the 40Gb/s and 100Gb/s domain. However, high power consumption, low link density and high cost seriously prevent traditional optical transceiver from being the next generation of optical link technology. For short reach communications, such as interconnects in supercomputers, the issues related to the existing electrical links become a major bottleneck for the next generation of High Performance Computing (HPC). Both applications are seeking for an innovative solution of optical links to tackle those current issues. In order to target the next generation of supercomputers and data communication, we propose to develop a high performance optical transmitter by utilizing CISCO Systems®\u27s proprietary CMOS photonic technology. The research seeks to achieve the following outcomes: 1. Reduction of power consumption due to optical interconnects to less than 5pJ/bit without the need for Ring Resonators or DWDM and less than 300fJ/bit for short distance data bus applications. 2. Enable the increase in performance (computing speed) from Peta-Flop to Exa-Flops without the proportional increase in cost or power consumption that would be prohibitive to next generation system architectures by means of increasing the maximum data transmission rate over a single fiber. 3. Explore advanced modulation schemes such as PAM-16 (Pulse-Amplitude-Modulation with 16 levels) to increase the spectrum efficiency while keeping the same or less power figure. This research will focus on the improvement of both the electrical IC and optical IC for the optical transmitter. An accurate circuit model of the optical device is created to speed up the performance optimization and enable co-simulation of electrical driver. Circuit architectures are chosen to minimize the power consumption without sacrificing the speed and noise immunity. As a result, a silicon photonic based optical transmitter employing 1V supply, featuring 20Gb/s data rate is fabricated. The system consists of an electrical driver in 40nm CMOS and an optical MZI modulator with an RF length of less than 0.5mm in 0.13&mu m SOI CMOS. Two modulation schemes are successfully demonstrated: On-Off Keying (OOK) and Pulse-Amplitude-Modulation-N (PAM-N N=4, 16). Both versions demonstrate signal integrity, interface density, and scalability that fit into the next generation data communication and exa-scale computing. Modulation power at 20Gb/s data rate for OOK and PAM-16 of 4pJ/bit and 0.25pJ/bit are achieved for the first time of an MZI type optical modulator, respectively

Cost benefit analysis of space communications technology. Volume 2: Final report

For abstract, see preceding accession

Engineering Ionomer Materials for Addressing Ohmic Resistances in Electrochemical Desalination and Waste Heat Recovery

Water scarcity and energy availability present important challenges that need to be addressed in the coming centuries. In the front of water technologies, desalting brackish water is of extreme importance for thermal electric power plants, chemical manufacturing plants, and other industrial operations that treat and reuse their water utilities. Membrane capacitive deionization (MCDI) is an energy efficient desalination technique that has drawn attention from commercial entities. Most material research studies on MCDI focus on enhancing electrode performance while little emphasis is given to rationale design of ion-exchange membranes (IEMs). In this work, the ionic conductivity, permselectivity, and thickness for three different IEM chemistries (polyaliphatic, poly (arylene ether), and perfluorinated) were correlated to MCDI performance attributes. A 5-10-fold reduction in area specific resistance (ASR), with unconventional perfluorinated and poly (arylene ether) IEMs reduced the energy expended per ion removed in MCDI by a factor of two, compared to conventional electrodialysis IEMs. For further advancement in energy efficiency of operation, ohmic resistance of the spacer channel needs to be addressed for which, ion-exchange resins bound by a polymeric binder termed resin wafers were explored. A new class of ion-exchange resin wafers (RWs) fabricated with ion-conductive binders were developed that exhibit exceptional ionic conductivities - a 3-5-fold improvement over conventional RWs containing a non-ionic polyethylene binder. Incorporation into a resin-wafer electrodeionization stack (RW-EDI) resulted in an increased desalination rate and reduced energy expenditure. Overall, this work demonstrates that ohmic resistances can be substantially curtailed with ionomer binder RWs at dilute salt concentrations. With respect to energy, thermally regenerative ammonia flow batteries (TRBs) are an emerging platform for extracting electrical energy from low-grade waste heat (T \u3c 130 °C). Previous TRB demonstrations suffered from poor heat to electrical energy conversion efficiency when benchmarked against state-of-the-art thermoelectric generators. This work reports the highest power density to date for a TRB (280 W m-2 at 55 °C) with a 5.7× improvement in power density over conventional designs and thermal efficiency (ηth) values as high as 2.99 % and 37.9 % relative to the Carnot efficiency (ηth/C). The gains made in TRB performance was ascribed to the zero gap design and deploying a low-resistant, inexpensive anion exchange membrane (AEM) separator and implementing a copper ion selective ionomer coating on the copper mesh electrodes. The improved TRB power density and the use of a low-cost materials represent significant milestones in low-grade waste heat recovery using electrochemical platforms

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development