Title page for ETD etd-04292010-204438

Type of Document

Master's Thesis

Author

Konakalla, Niharika

URN

etd-04292010-204438

Title

Adaptive Quantization in Wireless Sensor Networks with Encryption

Degree

Master of Science in Electrical Engineering (M.S.E.E.)

Department

Electrical & Computer Engineering

Advisory Committee

Advisor Name	Title
Naraghi-Pour, Morteza	Committee Chair
Liang, Xue-Bin	Committee Member
Wei, Shuangqing	Committee Member

Keywords

Wireless sensor networks
adaptive quantization
encryption

Date of Defense

2010-04-16

Availability

unrestricted

Abstract

We consider the estimation of a deterministic unknown parameter in an encrypted wireless sensor networks. Adaptive quantization is used on the sensor's observation and the outputs of the sensors are then encrypted using a probabilistic cipher. In a conventional fixed quantization scheme, estimation error grows exponentially with the difference between the threshold and the unknown parameter to be estimated. Hence, to avoid this, we used and adaptive quantization scheme where each sensor adaptively adjusts its quantization threshold.
We find the Cramer-Rao Lower Bound for the Ally Fusion Center (AFC) and then find the optimal estimate of the unknown parameter for the AFC. To find this, we first prove that the sequence of thresholds used for the quantization process forms a markov chain and that this chain is recurrent non-null and thus has a stationary distribution. This distribution is then obtained analytically in closed form as well as through numerical methods.
The optimal estimate of the unknown parameter for the AFC is obtained asymptotically in the number of sensors. The performance of the Third Party Fusion Center (TPFC) is only computed through simulation and compared to that of AFC.

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