Date of Award

Spring 2010

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical and Computer Engineering

Committee Director

Zia-ur Rahman

Committee Member

Dimitrie Popescu

Committee Member

Frederic D. McKenzie

Call Number for Print

Special Collections LD4331.E55 C3 2010

Abstract

Communication between deployed troops is very important on a battlefield. The real time knowledge of the location of the communicating patter is also very important in many situations because if you do not know the exact position of your units you cannot give correct orders. A minor error in an order can cause fatal results or lead to defeat. In many cases the position of the units is given through the speech channel by simply speaking the coordinates of the location. This can cause misunderstandings due to misinterpretation of the speech and makes it unsafe to rely on such communications. A more secure and robust technique is needed to convey the position of the talking side to the listening side.

In this thesis a system is designed that embeds GPS data into a speech signal using a speech watermarking technique. There are many speech watermarking techniques in the literature. Among these a novel audio watermarking technique is proposed. This technique is composed of spread-spectrum technique and Discrete Wavelet Transform (DWT) based technique. The watermark embedding mostly uses a DWT-based technique. In order to have a secure communication channel, the algorithm uses some aspects of spread-spectrum technique.

In the DWT-based embedding, the low frequency components of the speech signal are used to increase the robustness of the watermark to the channel noise. This causes some minor, but acceptable, changes in the quality of speech signal. The spread spectrum technique is used to secure the information that is embedded in the speech signal. In the spread-spectrum technique, we multiply the GPS data with a secret sequence that is generated by a secret key and generator algorithm. If the intruder does not know this sequence the data he gets is nothing more than a meaningless random sequence.

We analyze the robustness of the approach by using an additive white Gaussian noise (AWGN) for the channel noise and a characteristic fading channel. All the simulations are implemented in the MATLAB environment. The result is a watermarking technique that is robust and secure.

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DOI

10.25777/0gx5-k197

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