http://hdl.handle.net/1813/8272 Tue, 21 May 2013 00:24:33 GMT 2013-05-21T00:24:33Z http://ecommons.library.cornell.edu:80/retrieve/40059/EngQuad.gif http://hdl.handle.net/1813/8272 http://hdl.handle.net/1813/31515 Title: Two-Hop Interference Channels Impact of Linear Time-Varying Schemes Authors: Issa, Ibrahim; Fong, Silas L.; Avestimehr, Salman Abstract: We consider the two-hop interference channel (IC) with constant channel coefficients, which consists of two source-destination pairs, separated by two relays. We analyze the achievable degrees of freedom (DoF) of such network when relays are restricted to perform scalar amplify-forward (AF) operations, with possibly time-varying coefficients. We show that, somewhat surprisingly, by providing the flexibility of choosing time-varying AF coefficients at the relays, it is possible to achieve 4/3 sum-DoF. We also develop a novel outerbound that matches our achievability, hence characterizing the sum-DoF of two-hop interference channels with time-varying AF relaying strategies. Tue, 26 Feb 2013 00:00:00 GMT http://hdl.handle.net/1813/31515 2013-02-26T00:00:00Z http://hdl.handle.net/1813/10161 Title: GLOBAL POSITIONING SYSTEM STUDIES OF EQUATORIAL SCINTILLATIONS Authors: Theodore, Beach Abstract: The Global Positioning System (GPS) satellites provide an extensive array of beacon signals for probing the ionosphere. Studies of ionospheric propagation at the GPS L band frequencies (1.2 and 1.6 Hz) are of great interest for proposed communications satellite systems as well as for GPS itself. This dissertation describes the development and use of a specialized GPS receiver which measures signal strength at a high data rate (50 samples per second). The instrument monitors amplitude scintillations and the present application studies scintillations produced by propagation through equatorial ionospheric irregularities, particularly equatorial spread F. Several observations of GPS scintillations from stations near the geomagnetic equator (primarily Ancon, Peru) during equinox seasons are presented. Studies performed include drift measurements by correlation between spaced receivers and multiple instrument studies encompassing GPS scintillations, 50 MHz radar observations (at the Jicamarca Observatory) and 630 nm airglow images (from Arequipa, Peru). Observations of possible diffraction patterns generated by sharply defined differences in ionospheric electron density are also presented. Modeling suggests that the conditions required to obtain such patterns are gradients with widths of ~16 meters and a change in E or F-region total electron content (TEC) of about 1x10^16 electrons per m2, narrower and steeper than previous VHF observations of similar patterns imply. Finally, comparisons between TEC fluctuations, as measured by a dual-frequency GPS receiver, and GPS amplitude scintillations are made for collocated receivers at Ancon. Such comparisons are important because of the availability of global networks of GPS receivers which can be used to study TEC fluctuations at low sample rates (typically 30 seconds per sample). Several researchers currently conduct irregularity studies using the low rate TEC data from these networks, but the relationship between low-frequency TEC fluctuations and L band has not been investigated. This study concludes that, for the same line of sight, TEC fluctuations and scintillations are often related, and that relationship is explored here using a simple, one-dimensional phase screen model. Wed, 12 Mar 2008 15:31:44 GMT http://hdl.handle.net/1813/10161 2008-03-12T15:31:44Z http://hdl.handle.net/1813/8287 Title: Connections: Prospects for Future Research. Fall 2005 Editors: Linke, Simpson (Sam) Abstract: This 14th edition ot Connections features the results of the "SEERS Project," a challenge to the ECE faculty to examine their respective areas and attempt a forecast of possible new developments and prospects for future research. The thoughts of six faculty members who responded are recorded in the following pages. Future editions may contain predictions by other members of the faculty. The "Positive Feedback" section contains news of recent alumni activities. Sat, 01 Jan 2005 00:00:00 GMT http://hdl.handle.net/1813/8287 2005-01-01T00:00:00Z http://hdl.handle.net/1813/8286 Title: Connections: Computer Engineering Research. Spring 2004 Editors: Linke, Simpson (Sam) Abstract: This 13th edition of Connections features the challenging research of our computer engineering research group, updates the history of computer engineering in the EE/ECE School, and considers the impact on the ECE School of revisions in the computer engineering curriculum and of new analytical and experimental techniques in the discipline. The "Positive Feedback" section contains news of recent alumni activities. Thu, 01 Jan 2004 00:00:00 GMT http://hdl.handle.net/1813/8286 2004-01-01T00:00:00Z http://hdl.handle.net/1813/8285 Title: Connections: Biotechnology Research. Summer 2003 Editors: Linke, Simpson (Sam) Abstract: This twelfth edition of Connections features the challenging research of our biotechnology research group, relates the history of biotechnology in the EE/ECE School, and considers the impact on the ECE School of new analytical and experimental techniques in the biotechnology field. The "Positive Feedback" section contains news of recent alumni activities. Wed, 01 Jan 2003 00:00:00 GMT http://hdl.handle.net/1813/8285 2003-01-01T00:00:00Z http://hdl.handle.net/1813/8284 Title: Connections: Optoelectronic Technology Research. Summer 2002 Editors: Linke, Simpson (Sam) Abstract: This eleventh edition of Connections features the challenging research of our optoelectronic (OE) technology research group, relates the history of optoelectronic technology in the EE/ECE School, and considers the impact on the ECE School of new analytical and experimental techniques in the OE field. The "Positive Feedback" section contains news of recent alumni activities. Tue, 01 Jan 2002 00:00:00 GMT http://hdl.handle.net/1813/8284 2002-01-01T00:00:00Z http://hdl.handle.net/1813/8283 Title: Connections: Digital Signal Processing Research. Summer 2001 Editors: Linke, Simpson (Sam) Abstract: This tenth edition of Connections features the challenging research of our digital signal processing (DSP) research group, relates the history of computer technology in the EE/ECE School, and considers the impact of new analytical techniques in the DSP field on the ECE School. The "Positive Feedback" section contains news of recent alumni activities. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/1813/8283 2001-01-01T00:00:00Z http://hdl.handle.net/1813/8282 Title: Connections: Information Technology Research. Spring 2000 Editors: Linke, Simpson (Sam) Abstract: This ninth edition of Connections features the challenging research of our information technology research group, relates the history of control technology in the EE School, and considers the impact of new analytical techniques in the information technology field on the EE School. The "Positive Feedback" section contains news of recent alumni activities. Sat, 01 Jan 2000 00:00:00 GMT http://hdl.handle.net/1813/8282 2000-01-01T00:00:00Z http://hdl.handle.net/1813/8281 Title: Connections: Wireless Technology Research. Spring 1999 Editors: Linke, Simpson (Sam) Abstract: This eighth edition of Connections features the challenging research of our wireless technology research group, relates the history of wireless technology in the EE School, and considers the impact of new laboratories in this field on the EE School and the Department of Computer Science. The "Positive Feedback" section contains news of recent alumni activities. Fri, 01 Jan 1999 00:00:00 GMT http://hdl.handle.net/1813/8281 1999-01-01T00:00:00Z http://hdl.handle.net/1813/8280 Title: Connections: Semiconductor Research. Spring 1998 Editors: Linke, Simpson (Sam) Abstract: This seventh edition of Connections features the challenging research of our semiconductor and nanotechnology groups, relates the history of semiconductor technology in the EE School, and considers the impact of Duffield Hall on the future of these technologies in the EE School. The "Positive Feedback" section contains news of recent alumni activities. Thu, 01 Jan 1998 00:00:00 GMT http://hdl.handle.net/1813/8280 1998-01-01T00:00:00Z