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Browsing by Author "Morton, Yu, committee member"

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    Integration, characterization, and calibration of the high-frequency airborne microwave and millimeter-wave radiometer (HAMMR) instrument
    (Colorado State University. Libraries, 2014) Johnson, Thaddeus, author; Reising, Steven C., advisor; Morton, Yu, committee member; Vonder Haar, Thomas H., committee member; Kangaslahti, Pekka, committee member
    Current satellite ocean altimeters include nadir-viewing, co-located 18-34 GHz microwave radiometers to measure wet-tropospheric path delay. Due to the large antenna footprint sizes at these frequencies, the accuracy of wet path retrievals is substantially degraded within 40 km of coastlines, and retrievals are not provided over land. A viable approach to improve their capability is to add wide-band millimeter-wave window channels in the 90-183 GHz band, thereby achieving finer spatial resolution for a fixed antenna size. In this context, the upcoming Surface Water and Ocean Topography (SWOT) mission is in formulation and planned for launch in late 2020 to improve satellite altimetry to meet the science needs of both oceanography and hydrology and to transition satellite altimetry from the open ocean into the coastal zone and over inland water. To address wet-path delay in these regions, the addition of 90-183 GHz millimeter-wave window-channel radiometers to current Jason-class 18-34 GHz radiometers, is expected to improve retrievals of wet-tropospheric delay in coastal areas and to enhance the potential for over-land retrievals. To this end, an internally-calibrated, wide-band, cross-track scanning airborne microwave and millimeter-wave radiometer is being developed in collaboration between Colorado State University (CSU) and Caltech/NASA's Jet Propulsion Laboratory (JPL). This airborne radiometer includes microwave channels at 18.7, 23.8, and 34.0 GHz at both H and V polarizations; millimeter-wave window channels at 90, 130, 168 GHz; and temperature and water vapor sounding channels adjacent to the 118 and 183 GHz absorption lines, respectively. Since this instrument is demonstrating this technology for the potential use in future Earth science missions, substantial effort has been put into ensuring the instrument has a minimal mass and volume and is robust and well characterized. To this end the optical alignment has been extensively tested and characterized and a novel blackbody calibration target has been designed and integrated into the system. All supporting sub-systems such as power distribution and data acquisition have been integrated into the chassis allowing the instrument to be easily run by a single operator. Preliminary test flights have been done that demonstrate the reliability and robustness of this instrument as well as demonstrating the increased special resolution of the millimeter-wave window and sounding channels over that of the Jason-class 18-34 GHz radiometers.
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    Spectrum efficiency for future wireless communications
    (Colorado State University. Libraries, 2015) Yu, Bo, author; Yang, Liuqing, advisor; Luo, Jie, committee member; Morton, Yu, committee member; Wang, Haonan, committee member
    Spectrum efficiency has long been at the center of wireless communication research, development, and operation. Today, it is even more so with the explosive popularity of mobile internet, social networks, and smart phones that are more powerful than our desktops not long ago. As a result, there is an urgent need to further improve the spectrum efficiency in order to provide higher wireless data capacity. To respond to this demand, the 3rd Generation Partnership Project (3GPP) standardized the radio interface specifications for the next generation mobile communications system, called Long Term Evolution (LTE), in Release 8 specifications in 2008. Then the development continued and an enhanced LTE radio interface called LTE-Advanced (LTE-A) was standardized in Release 10 specifications in 2011. In order to ensure the sustainability of 3GPP radio access technologies over the coming decade, 3GPP standardization will need to continue identifying and providing new solutions that can respond to the future challenges. In this research, we investigate the potential technologies for further spectrum efficiency enhancement in the future steps of the standardization. One key direction is the further enhancement of local area technologies, which play a more and more important role in complementing the wide area networks. Specifically, we investigate two promising techniques for spectrum efficiency improvement in a macro-assisted small cell architecture, called the Phantom cell, which is proposed by DOCOMO. One is the possibility of dynamic allocation of subframes to uplink (UL) or downlink (DL) in time-division duplexing (TDD), called `Dynamic TDD'. The other is the more dynamic and flexible 3-dimensional (3D) beamforming which is facilitated by the adoption of active antenna systems (AAS) in BSs. In addition, full-duplex transmission and cooperative communication are two promising techniques known to enhance the spectrum efficiency of wireless communications. We focus on applying full-duplex in cooperative relaying networks and investigating the optimal resource allocation (both power and relay location) for full-duplex decode-and-forward (DF) relaying systems for spectrum efficiency enhancement.