http://hdl.handle.net/1721.1/7817 Tue, 21 May 2013 18:33:06 GMT 2013-05-21T18:33:06Z http://hdl.handle.net/1721.1/78536 MobiTest : an evaluation infrastructure for mobile distributed applications Sivaraman Kaushalram, Anirudh Sophisticated applications that run on mobile devices have become commonplace. Within the wide realm of mobile software applications there exists a significant number that make use of networking in some form. Unfortunately, such distributed mobile applications are inherently difficult to evaluate. Conventional evaluations of such distributed applications are limited to small, real-world deployments consisting of, perhaps, a handful of phones. Such tests often do not have the requisite number of users to produce the desired performance. Also, these experiments do not scale and are not repeatable. To address all these issues, we sought to evaluate distributed applications in a virtual environment. Besides being cheaper, such evaluations are reproducible and scale significantly better. This thesis documents our efforts in working towards this goal. We discuss the designs that we iterated through, along with the problems we faced in each of them. We hope these problems will inform future designs that can solve the challenges that we weren't able to solve efficiently. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 50-54). Sun, 01 Jan 2012 05:00:00 GMT http://hdl.handle.net/1721.1/78536 2012-01-01T05:00:00Z http://hdl.handle.net/1721.1/78535 Flying between obstacles with an autonomous knife-edge maneuver Barry, Andrew J. (Andrew James) We develop an aircraft and control system that is capable of repeatedly performing a high speed (7m/s or 16 MPH) "knife-edge" maneuver through a gap that is smaller than the aircraft's wingspan. The maneuver consists of flying towards a gap, rolling to a significant angle, accurately navigating between the obstacles, and rolling back to horizontal. The speed and roll-rate required demand a control system capable of highly precise, repeatable maneuvers. We address the necessary control theory, path planning, and hardware requirements for such a maneuver, and give a proposal for a new system that may improve upon the existing techniques. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 55-58). Sun, 01 Jan 2012 05:00:00 GMT http://hdl.handle.net/1721.1/78535 2012-01-01T05:00:00Z http://hdl.handle.net/1721.1/78476 Surface functionalization of graphene devices Zhang, Xu, S.M. Massachusetts Institute of Technology Graphene, a zero-gap semiconductor with massless charge carriers, is emerging as an amazing material for future electronics, due to its outstanding electrical and mechanical performances. However, the lack of a bandgap results in a high off-state current leakage and a nonsaturating drive current, both of which severely limit graphene's practical applications in electronic devices. Chemical functionalization on its surface promises a powerful tool to manipulate its electronic properties and modify its atomic structures. Graphene is a true two-dimensional material; every carbon atom in single layer graphene is exposed to its environment. Therefore, the surface functionalization in graphene can significantly change its physical and chemical properties, such as bandgap opening and piezoelectricity engineering, etc. Hydrogenation and fluorination have been experimentally demonstrated to be effective in changing the hybridization state of carbon atoms and opening a bandgap from 2.9 eV to 5.4 eV. However, both of these methods are destructive to graphene, and will degrade its carrier mobility. In this study, we fabricated graphene-based field effect transistors (FETs) and conducted surface functionalization via plasma reactions. We systematically investigated graphene chlorination and characterized the results with Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy (AFM) and transport measurement. A schematic picture of how the chlorine plasma interacts with graphene was also proposed. Hydrogenation and fluorination were also conducted and analyzed as comparison. We demonstrated that chlorination in graphene via plasma reactions is a very effective and controllable way to engineer its structural and electronic properties. The high mobility of the resulting structures is a very important advantage with respect to other functionalization approaches. Keywords: Graphene, functionalization, chlorination, plasma, bandgap, Fermi level, doping, mobility Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 114-117). Sun, 01 Jan 2012 05:00:00 GMT http://hdl.handle.net/1721.1/78476 2012-01-01T05:00:00Z http://hdl.handle.net/1721.1/78475 Amplitude and phase modulation techniques for an asymmetric multi-level outphasing transmitter Yahalom, Gilad New techniques for improving outphasing transmitters show potential of breaking the traditional linearity-efficiency trade-off by using highly efficient non-linear switching Power Amplifiers (PAs). This work focuses on two of the main building blocks of modem outphasing systems, the power supply switching network and the phase modulator. Both are ubiquitous building blocks in modern RF transceivers, and both are especially critical in Asymmetric Multilevel Outphasing (AMO) systems. A design of the power supply network and control scheme is proposed for an implementation in mm-wave operating frequencies as part of a complete transmitter in 45nm SOI CMOS utilizing four discrete power supplies and achieving data rates of up to 4GS/s. The design includes analysis and simulation of the control signal data path requirements for optimal system operation as well as switch optimization and effects of the driving strength on overall system performance. A new design concept is proposed for a phase modulator utilizing the phase shifthing capabilities of a resonant tank and the ability to seperately control the circuit properties via its components. A prototype in 65nm CMOS achieves 12 bits of resolution, with an Effective Number Of Bits (ENOB) of 10.2 bits and very fast settling time of less than 5 carrier cycles. The chip is also tested as a stand alone transmitter showing an EVM of less than 5% for 8-PSK modulation at maximum data rate, meeting the requirements for operation at the Medical Implant Communication Services (MICS) band. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 93-95). Sun, 01 Jan 2012 05:00:00 GMT http://hdl.handle.net/1721.1/78475 2012-01-01T05:00:00Z