Thèse de doctorat : Informatique : Evry-Val d'Essonne : 2009. / Titre provenant de l'écran-titre.

Thèse de doctorat : Informatique : Evry-Val d'Essonne : 2009. / Titre provenant de l'écran-titre.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): McEachen, John C. ; Loomis, Herschel H. Second Reader: Garcia, Vicente C. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: 802.16, WiMAX, geolocation, ranging, timing adjust. Includes bibliographical references (p. 71-72). Also available in print.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Geoffrey Xie. Includes bibliographical references (p. 131-132). Also available online.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2003. / Thesis advisor(s): Tri T. Ha, Jan E. Tighe. Includes bibliographical references (p. 105). Also available online.

Almost all mobile devices nowadays are enabled with IEEE 802.11 Wireless Local Area Network (WLAN), which is also known as WiFi. One of the most important considerations when choosing an 802.11 device is its battery life. To allow mobile devices to conserve energy, IEEE 802.11 standard specifies a power save mode (PSM). A station/device in PSM, i.e. PSM-STA, will wake up at a predefined listen interval (LI) to receive frames buffered at the access point (AP) while it is sleeping. In this thesis, we focus on enhancing the basic PSM mechanisms in the standard. In particular, two new power saving schemes, delayed wakeup and dynamic listen interval, are proposed. Unlike many existing schemes, our schemes are fully standard compliant, and legacy devices can support them via a firmware upgrade. In our delayed wakeup (DW) scheme, we assume that all PSM-STAs use the same listen interval of one. That is all PSM-STAs wake up at every beacon frame broadcast, or beacon interval (BI). From the traffic indication map (TIM) in the beacon, a PSMSTA learns if there are any buffered frames at AP. If yes, it will stay awake until all buffered frames are retrieved. This creates a rush hour on the shared channel right after a beacon broadcast. If the channel is congested, having all PSM-STAs staying awake will not improve the system delay performance but consume more power. Aiming at saving battery power while not affecting delay-throughput performance, our DWscheme divides a BI into n sub-BIs. Then based on the amount of buffered frames, AP identifies and instructs “excess” stations to sleep immediately and wake up at a non-congested sub-BI later on. “Instructions” are judiciously encoded inside the modified TIM. We show that our modifications are fully transparent to legacy stations. In order to more accurately identify the amount of excess stations, an analytical model is also constructed to derive the saturated throughput of a WLAN consisting of PSM-STAs. In our dynamic listen interval (DLI) scheme, we aim at minimizing unnecessary wakeups while without sacrificing delay performance. Note that when a PSM-STA wakes up to receive a beacon and found that there are no buffered frames at AP, the PSM-STA experiences an unnecessary wakeup. Accordingly, the associated mode transition energy is wasted. According to the IEEE 802.11 standard, each STA chooses its fixed LI at the time of association. If LI=1, a STA wakes up at every beacon interval (as that in DW scheme). Although packet delay is minimized in this case, the chance of unnecessary wakeups can be high. On the other hand, a larger LI can reduce the chance of unnecessary wakeups but the delay will be increased. Our DLI scheme addresses this problem by dynamically adjusting the LI value according to traffic load. Specifically, each unnecessary wakeup will increase a STA’s LI by one, and a necessary wakeup will immediately reset LI to one. Simulations show that when traffic is bursty, mode transition energy consumption can be reduced without noticeable degradation in delay performance. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / The wireless acquisition system LISA has been designed for mechanical phenomenon analysis onboard aircrafts. It has been in use for more than one year now. This paper describes the organization of this equipment and the experiences related by first users.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / Network switches are a critical component in any networked FTI data acquisition system in order to allow the forwarding of data from the DAU to the target destination devices such as the network recorder, PCM gateways, or ground station. Larger configurations require one or more switch boxes to handle aggregation, routing, filtering and synchronization via the IEEE 1588 Precision Time Protocol. However, for smaller configurations where space and weight restrictions are more stringent, a separate switch box may not be practical This paper discusses how all the essential features of an FTI network, such as flexible forwarding and filtering and IEEE 1588 synchronization, can be maintained without the need for the separate switch box thus making significant savings on weight and size and reducing cost.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / The NASA Remote Imaging System Acquisition (RISA) project is a prototype camera intended to be used by future NASA astronauts. NASA has commissioned the development of this engineering camera to support new mission objectives and perform multiple functions. These objectives require the final prototype to be radiation hardened, multispectral, completely wireless in data transmission and communication, and take high quality still images. This year's team was able to successfully develop an optical system that uses a liquid lens element for focus adjustment. The electrical system uses an Overo Fire computer-on-module (COM) developed by Gumstix. The OMAP processor onboard handles all communication with a monochromatic CMOS sensor, liquid lens control circuitry, pixel data acquisition and processing, and wireless communication with a host computer.

M. Tech. Electrical Engineering. / Discusses the study as limited to the formal specification/modelling and formal verification of protocols proposed and applicable to the initial network entry procedure in WiMAX networks. Secondly, formal specification of the existing protocols under consideration will be based on their informal specification available in the literature and not on proprietary protocols for which little or no information is available. Thirdly, this research work does not intend to wipe out the state space explosion problem but rather applies existing optimization techniques to supress it. Finally, the study does not assess the usability performance impact of the proposed security scheme and thus recommends that this analysis should be done as future work to evaluate the functionality and soundness of deploying the proposed security scheme.