ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / The goal of the project described in this paper, is to develop a platform for undergraduate engineering students to use in system analysis and design courses. We chose to develop an inexpensive robotic platform. The robot is intended to be autonomous, under the control of an on-board microcontroller. In the first revision of the hardware, a three wheeled design will be used, with the intention of being used indoors, on smooth surfaces. Students in their first year of college education will purchase the components, and assemble the robot. After analyzing the baseline design, they will be encouraged to incorporate new sensors and actuators in the subsequent laboratory courses.

Recently, wireless network technology has grown at such a pace that scientific research has become a practical reality in a very short time span. One mobile system that features high data rates and open network architecture is 4G. Currently, the research community and industry, in the field of wireless networks, are working on possible choices for solutions in the 4G system. The researcher considers one of the most important characteristics of future 4G mobile systems the ability to guarantee reliable communications at high data rates, in addition to high efficiency in the spectrum usage. On mobile wireless communication networks, one important factor is the coverage of large geographical areas. In 4G systems, a hybrid satellite/terrestrial network is crucial to providing users with coverage wherever needed. Subscribers thus require a reliable satellite link to access their services when they are in remote locations where a terrestrial infrastructure is unavailable. The results show that good modulation and access technique are also required in order to transmit high data rates over satellite links to mobile users. The dissertation proposes the use of OFDM (Orthogonal Frequency Multiple Access) for the satellite link by increasing the time diversity. This technique will allow for an increase of the data rate, as primarily required by multimedia applications, and will also optimally use the available bandwidth. In addition, this dissertation approaches the use of Cooperative Satellite Communications for hybrid satellite/terrestrial networks. By using this technique, the satellite coverage can be extended to areas where there is no direct link to the satellite. The issue of Cooperative Satellite Communications is solved through a new algorithm that forwards the received data from the fixed node to the mobile node. This algorithm is very efficient because it does not allow unnecessary transmissions and is based on signal to noise ratio (SNR) measures.

Augmented reality systems are ones which insert virtual content into a user’s view of the real world, in response to environmental conditions and the user’s behavior within that environment. This virtual content can take the form of visual elements such as 2D labels or 3D models, auditory cues, or even haptics; content is generated and updated based on user behavior and environmental conditions, such as the user’s location, movement patterns, and the results of computer vision or machine learning operations. AR systems are used to solve problems in a range of domains, from tourism and retail, education and healthcare, to industry and entertainment. For example, apps from Lowe’s [82] and Houzz [81] support retail transactions by scanning a user’s environment and placing product models into the space, thus allowing the user to preview what the product might look like in her home. AR systems have also proven helpful in such areas as aiding industrial assembly tasks [155, 175], helping users overcome phobias [35], and reviving interest in cultural heritage sites [163]. Mobile AR systems are ones which run on portable handheld or wearable devices, such that the user is free to move around their environment without restric- tion. Examples of such devices include smartphones, tablets, and head-mounted dis- plays. This freedom of movement and usage, in combination with the application’s reliance on computer vision and machine learning logic to provide core function- ality, make mobile AR applications very difficult to test. In addition, as demand and prevalence of machine learning logic increases, the availability and power of commercially available third-party vision libraries introduces new and easy ways for developers to violate usability and end-user privacy. The goal of this dissertation, therefore, is to understand and mitigate the challenges involved in testing mobile AR systems, given the capabilities of today’s commercially available vision and machine learning libraries. We consider three related challenge areas: application behavior during unconstrained usage conditions, general usability, and end-user privacy. To address these challenge areas, we present three research efforts. The first presents a framework for collecting application performance and usability data in the wild. The second explores how commercial vision libraries can be exploited to conduct machine learning operations without user knowledge. The third presents a framework for leveraging the environment itself to enforce privacy and access control policies for mobile AR applications. / Computer and Information Science

[pt] Existe um crescente interesse na introdução de serviços integrados no ambiente de comunicações móveis e sem fio. Estes serviços podem incluir, em alguns casos, informação na forma de áudio, vídeo, imagens e dados simultaneamente junto com o serviço existente de voz nas redes celulares. Devido à necessidade por maior faixa, o aumento da capacidade da interface rádio continuará sendo um dos principais requisitos para a introdução destes novos serviços. Para atender esta necessidade, vários métodos de acesso estão sendo propostos. Esta tese propõe um novo protocolo de acesso, D-RAMA, que visa extender os métodos de acesso determinísticos TRAMA e FRAMA. A validação do algoritmo é feita por meio de simulação considerando diversas interfaces rádio, assim como diferentes tipos de tráfegos. / [en] Third generation systems will present several new enhancements while compared with current second generation technologies. Some of the most important ones are the support of integrated services (audio, video, data) as well as speech, operation in different radio environments with several propagation conditions and increased capacity. These features demand an efficient media access control (MAC) protocol, supporting both Constant Bit Rate (CBR) and Variable Bit Rate (VBR) traffic types with different Quality of Service (QoS) requeriments. In order to supply this demand, several packet access methods are being proposed. This thesis presents a new media access protocol, D-RAMA (Dynamic Priorities Resource Auction Multiple Access) and FRAMA (Fair resource Auction Multiple Access) methods, and is designed to fulfill the requirements of third generation systems. The protocol is validated through simulations, considering several radio interfaces and traffic sources.

No description available.

<div><p>Modern mobile devices have numerous ephemeral tasks. These tasks are driven by background activities, such as push notifications and sensor readings. In order to execute these tasks, the whole platform has to periodically wake up beforehand, and go to sleep afterwards. During this process, the OS kernel operates on power state of various IO devices, which has been identified as the bottleneck for energy efficiency. To this end, we want to offload this kernel phase to a more energy efficient, microcontroller level core, named peripheral core.</p></div><div><p> </p></div><div><p>To execute commodity OS on a peripheral core, existing approaches either require much engineering effort or incur high execution cost. Therefore, we proposed a new OS model called transkernel. By utilizing cross-ISA dynamic binary translation (DBT) technique, transkernel creates a virtualized environment on the peripheral core. It relies on a small set of stable interfaces. It is specialized for frequently executed kernel path. It exploits ISA similarities to reduce DBT overhead.</p></div><div><p> </p></div><div><p>We implement a transkernel model on ARM platform. With novel design and optimization, we demonstrate that a transkernel can gain energy efficiency. Moreover, it provides a new OS design to harness heterogeneous SoCs.</p></div>

Mobility in distributed object systems is useful as it can provide such properties as load balancing, code to data movement, fault tolerance, migration to stable storage, and autonomous semantics. In a widely distributed system, these properties are important as they can help alleviate latency issues and increase performance within the system. Additionally, they provid more flexibility in the programming of distributed systems by relaxing static location restrictions. Location transparency removes the need for client objects to explicitly know or define the location of a server object when communicating. If a server object is capable of migration, relocation transparency maintains reference validity throughout the migration. Several models for providing relocation transparency exist, including the home location, forwarding location, and broadcast models. This thesis proposes a model that uses a distributed registry system and dynamic reference updating to provide location and relocation transparency. A registry system is used to provide location independence by resolving a location independent name to a reference that can be used by a client. A naming system is used to provide correct binding and production of names within the naming restrictions of the system. The thesis proposes that the choice of naming system within a distributed or mobile object system has a large effect on the system's ability to support efficient transparent object relocation. This thesis proposes that a formal analysis of naming systems enables the selection of an appropriate naming system for a distributed or mobile object system given the object system's naming, distribution and transparency requirements. This thesis presents a new classification scheme for naming systems, based on analysis of a broad spectrum of naming systems. A classification of existing mobile and distributed object systems with respect to existing naming models is provided. It is shown that the current models need to be refined and extended to completely and correctly classify the example systems. This thesis proposes extensions and refinements that enable correct and complete classification of mobile and distributed object systems with a need for transparency. The extended naming model is then used to describe a naming system that is capable of implementing any naming system classifiable by the extended model. A classification of a naming system to support the proposed model of location and relocation transparency is presented. A distributed ORB system is designed and implemented to support the distributed namespace and generic naming system implementation. The distributed ORB system is hierarchically structured and is capable of adapting in response to node failure. This ORB system is used to support client and server object integration in the DISCWorld metacomputing environment. The ORB system is used to provide migration, replication and cloning services to the DISCWorld metacomputing environment. A qualitative analysis of the generic naming system and the DISCWorld ORB system is performed. A comparison between the proposed model for location and relocation transparency and existing models is also presented. This comparison shows that the proposed model exhibits better location and relocation performance within the DISCWorld environment. The distributed nature of the ORB system and namespace provides a scalable nature in terms of namespace size, the number of objects within the system, and the frequency of location and relocation requests. / Thesis (Ph.D.)--Engineering (Department of Computer Science), 2000.

Mobile systems, such as ground robots and electric vehicles, inherently operate in stochastic environments where load demands are largely unknown. Onboard energy storage, most commonly an electrochemical battery system, can significantly constrain operation. As such, mission planning and control of mobile systems can benefit from a priori knowledge about battery dynamics and constraints, especially the rate-capacity and recovery effects. To help overcome overly conservative predictions common with most existing battery remaining run-time algorithms, a prediction scheme was proposed. For characterization of a priori unknown power loads, an unsupervised Gaussian mixture routine identifies/clusters the measured power loads, and a jump-Markov chain characterizes the load transients. With the jump-Markov load forecasts, a model-based particle filter scheme predicts battery remaining run-time. Monte Carlo simulation studies demonstrate the marked improvement of the proposed technique. It was found that the increase in computational complexity from using a particle filter was justified for power load transient jumps greater than 13.4% of total system power. A multivariable reliability method was developed to assess the feasibility of a planned mission. The probability of mission completion is computed as the reliability integral of mission time exceeding the battery run-time. Because these random variables are inherently dependent, a bivariate characterization was necessary and a method is presented for online estimation of the process correlation via Bayesian updating. Finally, to abate transient shutdown of mobile systems, a model predictive control scheme is proposed that enforces battery terminal voltage constraints under stochastic loading conditions. A Monte Carlo simulation study of a small ground vehicle indicated significant improvement in both time and distance traveled as a result. For evaluation of the proposed methodologies, a laboratory terrain environment was designed and constructed for repeated mobile system discharge studies. The test environment consists of three distinct terrains. For each discharge study, a small unmanned ground vehicle traversed the stochastic terrain environment until battery exhaustion. Results from field tests with a Packbot ground vehicle in generic desert terrain were also used. Evaluation of the proposed prediction algorithms using the experimental studies, via relative accuracy and [alpha]-[lambda] prognostic metrics, indicated significant gains over existing methods. / text

JavaScript has permeated into every aspect of the web experience in today's world, making it highly crucial to process it as quickly as possible. With the proliferation of HTML5 and its associated mobile web applications, the world is slowly but surely moving into an age where majority of the webpages will involve complex computations and manipulations within the JavaScript engine. Recent techniques like Just-in-Time (JIT) compilation have become commonplace in popular browsers like Chrome and Firefox, and there is an ongoing effort to further optimize them in the context of mobile systems. In order to fully take advantage of JavaScript-heavy webpages, it is important to first characterize the interaction of these webpages (both existing pages and modern HTML5 pages) with the different components of the JavaScript engine, viz. the interpreter, the method JIT, the optimizing compiler and the garbage collector. In this thesis, the aforementioned characterization work was leveraged to identify the limits of JavaScript optimizations. Subsequently, a particular optimization, i.e. Register Allocation heuristics was explored in detail on different types of JavaScript programs. This was primarily because the majority of the time (an average of 52.81%) spent in the optimizing compiler is for the register allocation stage alone. By varying the heuristics for register assignment, interval priority and spill selection, a clear idea is obtained about how it impacts certain types of programs more than others. This thesis also gives a preliminary insight into JavaScript applications and benchmarks, showing that these applications tend to be register-intensive, with large live intervals and sparse uses, and sensitive to array and string manipulations. A statically-selected optimal register allocation scheme outperforms the default register allocation scheme resulting in 9.1% performance improvement and 11.23% reduction in execution time on a representative mobile system. / text

Τα συστήματα κινητής τηλεφωνίας απαιτούν οι κινητές συσκευές να βρίσκονται στην περιοχή κάλυψης ενός σταθμού βάσης για να μπορεί να διεξαχθεί επικοινωνία. Τι συμβαίνει όμως όταν ένα κινητό τερματικό βρεθεί σε περιοχή που δεν καλύπτεται από σταθμό βάσης; Αυτό μπορεί να συμβεί είτε σε περίπτωση που η περιοχή είναι απομονωμένη ώστε να μη έχει καταστεί συμφέρον να αναπτυχθεί υποδομή κινητής επικοινωνίας, είτε αν βρίσκεται στην επικράτεια υποανάπτυκτης χώρας όπου οι υποδομές είναι απαρχαιωμένες ή ανύπαρκτες, είτε οι υποδομές της περιοχής έχουν καταστραφεί ή καταστεί πρακτικά μη λειτουργικές λόγω απρόσμενων συμβάντων (πόλεμοι, σεισμοί, παλίρροιες, κλπ). Τα κινητά συστήματα δορυφορικών επικοινωνιών αναπτύχθηκαν ακριβώς για να παρέχουν αξιόπιστες υπηρεσίες επικοινωνιών «παντού και πάντοτε». Ειδικά, την δεκαετία 1990 που άρχισε η ευρεία χρήση κινητών επικοινωνιών, αντιμετωπίστηκε το αρχικά το πρόβλημα περιορισμένης κάλυψης λόγω μη επαρκούς επίγειας υποδομής. Η ιδέα ήταν να εξυπηρετούνται οι συνδρομητές από δορυφόρους αντί σταθμών βάσης, οι οποίοι θα παρείχαν παγκόσμια κάλυψη και θα παρέμειναν ανεπηρέαστοι από τις εξελίξεις στην Γη. Συνεπώς, δεν θα απαιτούνταν πρόσθετες υποδομές για κάλυψη περιοχών αλλά οι αρχικοί αστερισμοί δορυφόρων να παρείχαν αδιάκοπη κάλυψη. Ωστόσο λόγω της υψηλής χρέωσης δορυφορικής επικοινωνίας, της αδυναμίας παροχής εξαρχής των διαφημιζόμενων υπηρεσιών και του ανταγωνισμού από τα επίγεια συστήματα κινητής τηλεφωνίας, κάποια από τα δορυφορικά κινητά συστήματα (Iridium, Globalstar) οδηγήθηκαν σε χρεωκοπία στις αρχές της δεκαετίας 2000. Τα συστήματα αυτά εξαγοράστηκαν και ανασυστάθηκαν, και εξυπηρετούν εκατοντάδες χιλιάδων συνδρομητών, ενώ ετοιμάζονται για την εκτόξευση νέας γενεάς δορυφόρων. Η παρούσα διπλωματική εργασία πραγματεύεται τις τεχνικές διαφορικής λήψης στα συστήματα κινητών δορυφορικών επικοινωνιών και γίνεται προσομοίωση της διαφορικής λήψης σήματος δορυφόρου από πλευράς χρήστη. Για να καταστούν όμως σαφέστερες στον χρήστη οι τεχνικές αυτές, προηγείται επισκόπηση των αρχών επικοινωνίας και της αρχιτεκτονικής των συστημάτων αυτών, ενώ μελετώνται και τεχνικές επεξεργασίας που εφαρμόζονται στο κινητό δορυφορικό σήμα. Συγκεκριμένα, στο Κεφάλαιο 1, αναφέρονται οι αρχές κινητών δορυφορικών επικοινωνιών, δηλαδή η συχνότητες επικοινωνίας, οι τροχιές των δορυφόρων, τα φαινόμενα διάδοσης στο ασύρματο δορυφορικό μονοπάτι, η κάλυψη των δορυφόρων κινητών επικοινωνιών, οι δορυφορικές ζεύξεις και οι τεχνικές μεταπομπής του κινητού σήματος. Στο Κεφάλαιο 2, αναλύεται η αρχιτεκτονική των δορυφορικών συστημάτων κινητών επικοινωνιών, δηλαδή όλες οι συνιστώσες διαστήματος και εδάφους από τις οποίες απαρτίζεται ένα δορυφορικό σύστημα που επιτελεί υπηρεσίες κινητών επικοινωνιών. Έμφαση δίνεται στα υποσυστήματα του τηλεπικοινωνιακού δορυφόρου που αποτελεί την κεντρική συνιστώσα κάθε δορυφορικού συστήματος. Γίνεται αναφορά και στην επίγεια υποδομή που παρέχει υποστήριξη στους δορυφόρους και διασύνδεση με τα άλλα δίκτυα επικοινωνιών. Ακολουθεί περιγραφή της αρχιτεκτονικής των δύο πιο δημοφιλών δορυφορικών συστημάτων υπηρεσιών κινητών επικοινωνιών, Iridium και Globalstar. Πλέον όλα τα σήματα κινητών επικοινωνιών είναι ψηφιακά, καθότι η ψηφιακή τεχνολογία προσφέρει πολλά πλεονεκτήματα έναντι της αναλογικής. Στο Κεφάλαιο 3, αναλύονται οι ψηφιακές τεχνικές που εφαρμόζονται στο δορυφορικό σήμα κινητών επικοινωνιών ακολουθώντας όλα τα στάδια από την ψηφιοποίηση του αναλογικού σήματος που παράγεται από τον ομιλητή, τις διάφορες μορφές κωδικοποίησης, πολυπλεξίας, διαμόρφωσης και τέλος, πολλαπλής πρόσβασης στον δορυφορικό αναμεταδότη. Το Κεφάλαιο 4 μπαίνει στην καρδιά της διπλωματικής εργασίας, δηλαδή τις τεχνικές διαφορισμού. Αναφέρονται γενικά οι τεχνικές διαφορισμού πομπού και δέκτη, και ο δέκτης RAKE για διαφορική λήψη κινητού τηλεφώνου. Επιπλέον αναλύονται οι διαδικασίες διαφορισμού που λαμβάνουν χώρα σε όλο το εύρος ενός δορυφορικού συστήματος κατά την διεξαγωγή κλήσης, που εμπλέκουν δύο ή περισσότερες πύλες και δύο ή περισσότερους δορυφόρους. Τέλος, στο Κεφάλαιο 5, γίνεται προσομοίωση της διαφορικής λήψης τηλεφωνικού σήματος CDMA που εκπέμπεται από πολλαπλούς δορυφόρους που βρίσκονται εντός του οπτικού πεδίου ενός δορυφορικού τηλεφώνου. Τα σήματα των δορυφόρων λαμβάνονται από τον δέκτη RAKE του τηλεφώνου και συνδυάζονται σε ένα συνεκτικό σήμα με κάποια τεχνική συνδυασμού. Βάσει των αποτελεσμάτων των προσομοιώσεων θα αξιολογηθεί η ποιότητα του λαμβανόμενου σήματος για κάθε πρόσθετο δορυφόρο και για κάθε τεχνική συνδυασμού διαφορισμού. / The mobile satellite systems were developed with the ambitious goal to provide reliable service “anywhere, anytime”. Whereas the cellular mobile systems depend on ground infrastructure in order to be operational, the mobile satellite systems indeed can still work even where ground infrastructure is inadequate or destroyed by unexpected events such as earthquakes, tides or wars. The concept of mobile satellite systems is that mobile satellite phones communicate directly with a fleet of dozens of satellites just like cell phones communicate with base stations. In such a way, communication can be delivered uninterrupted by events on Earth, as well as the need for additional ground infrastructure can be bypassed. However, due to high satellite service charges, inability to provide the advertised services and high competition from terrestrial cellular systems some of mobile satellite systems (Iridium, Globalstar) fell into bankruptcy in early 2000s. These systems were taken over and reestablished and are currently serving hundreds of thousands customers, while been prepared to launch a new generation of satellites. The purpose of the present diploma thesis is to study the reception techniques in the mobile satellite systems. Eventually, the diversity reception is simulated for the case of a satellite phone receiving signal from four LEO satellites, inspired by the Globalstar system. In order that the function of a MSS can be understood, before the presentation of the simulation, the principles of mobile satellite communications are presented, following the architecture of an MSS and the digital signal techniques that are utilized in mobile satellite communications. Specifically, in Chapter 1 the principles of mobile satellite communications are reviewed. We start with the types of mobile satellite services and frequency allocation. Then the communications satellites orbits are mentioned with emphasis to the advantages and disadvantages of each orbit that determines its utilization in satellite communications. We proceed with the mobile satellite links, the coverage of a LEO satellite and the handover techniques that are necessary in order to guarantee uninterrupted connection and seamless switching during a call. In Chapter 2, the architecture of a mobile satellite system is analyzed, i.e. the components of which a mobile satellite system is comprised. At first, we will take an insight in the structure and the various systems of a communications satellite. In addition, we will see the structure of the ground segment that supports the satellites and the user segment. Additionally the Iridium and Globalstar are presented that follow totally opposite philosophies in all implementation and function aspects. Digital technology has managed to prevail over its analog counterpart in most satellite communications thanks to its inherent advantages. The most common digital signal techniques will be reviewed in Chapter 3 concerning the MSS. Specifically, source coding, channel coding, line coding, modulation, multiplexing, multiple access, pulse shaping, and equalization techniques are taken into account since all these techniques are implemented in almost every wireless digital communication, rendering the digital signal resistant to wireless channel impairments as well as bandwidth effective. In Chapter 4, diversity analysis takes place. Diversity is a technique whereby multiple replicas of a signal are sent over a wireless channel so as to mitigate fading. We will see the various diversity techniques along with the diversity combining techniques which are used to finally combine the received signals into a single coherent signal. Furthermore, a reader will learn about some diversity techniques used in mobile satellite systems involving multiple satellites and gateways during call establishment and routing. Finally, the knowledge acquired from the previous chapters will help understand the process of diversity reception in the case of a satellite phone. In Chapter 5, the signal reception by a satellite phone from four LEO satellites is simulated by use of the Matlab programming tool. Every satellite is presumed to transmit a replica of the same signal based on the CDMA spread spectrum technique whereas the signals arrive at the phone following different paths (path diversity). Hence the received signal is comprised of four multipath components arriving at the receiver at different times. The satellite phone includes a RAKE receiver which is composed of four fingers or braches each synchronized to a multipath component. The RAKE receiver combines the multipath components using each of the SC, EGC and MRC techniques. Conclusively, the signal-to-noise ratio (SNR) and energy per bit to noise power spectral density ratio (Eb/N0) are measured as a function of the number of RAKE receiver fingers and the combining technique. The simulation results will denote the importance of diversity in the quality of the received signal in a multipath environment as well as the efficiency of each of the combining techniques.