TitlePHY-techniques to improve higher-layer functions in wireless networks
NameXiao, Liang (author), Mandayam, Narayan (chair), Trappe, Wade (internal member), Greenstein, Larry (internal member), Valenzuela, Reinaldo (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectElectrical and Computer Engineering,
Wireless sensor networks,
Wireless communication systems
DescriptionThe wireless medium contains location-specific
information at various scales, and thus it can serve in multiple ways to enhance the performance of wireless networks. In this thesis we study the use of physical-layer information to improve higher-layer functions in the following categories: (1) the use of
the measured large-scale channel gain variations (due to power spreading and shadowing) to estimate signal outage and to perform mobile localization; and (2) the use of the measured small-scale channel gain variations (due to multipath) to improve wireless network security.
We first consider sensor networks that record received signal strength for estimating and updating network performance. Using a generic path-loss model incorporating distance effects and shadow fading, we apply the principle of importance sampling to the sensor placements. This helps to minimize measurement costs while accurately estimating outage probability and coverage holes, thereby improving the radio resource management of wireless systems. We also analyze the use of sensor networks to locate
mobiles, and we propose four simple-yet-accurate localization algorithms that meet E-911 requirements in most environments. The localization performance can be further improved by implementing a minimum mean square error (MMSE) algorithm which meets the
Cramer-Rao lower bound. However, the four simple proposed algorithms have much lower numerical complexity than MMSE for real-time operation and require little a priori knowledge of the channel parameters.
Next, we exploit the rapid-decorrelation property of the multipath channel to enhance security in environments with rich scattering. We propose a channel-based authentication scheme to detect both spoofing attacks (a spoofing node pretends to be another node to gain access to network resources); and Sybil attacks (a Sybil node maliciously sends multiple service requests with different identities, in hopes of depleting network resources). The scheme uses little additional system overhead, as it exploits pilots or preambles that already exist in most wireless systems. A double-layer authentication protocol is devised, whereby the scheme either combines with higher-layer security mechanisms, such as 802.11i or works independently with some performance degradation. Verification that PHY-based authentication provides good performance is performed using several methods, specifically,
stochastic channel modeling, site-specific ray-tracing and field tests.
NoteIncludes bibliographical references (p. 125-129)
Noteby Liang Xiao
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.