Thesis (M.S.)--Ohio University, June, 2004. / Includes bibliographical references (p. 94-95).

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [116]-119).

Thesis (M. Eng.)--Carleton University, 1989. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--Carleton University, 1992. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--Carleton University, 1993. / Also available in electronic format on the Internet.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 103-109). Also available in electronic version.

Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (p. 94-95)

Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 81-83)

Many industries are turning to wireless communication systems to track their assets. One example of such an industry is the shipping industry, where — under the growing emphasis on homeland security — tracking cargo containers and their contents has become a high priority. There are several beacons on the commercial market that will meet this need if the required beacon does not need to be independently powered or to have global coverage. This thesis attempts to find a design solution for a beacon that transmits location data, is battery powered, and has world-wide coverage. The beacon is intended to be a low power, transmit only device, and the receiver will not be designed to operate in real-time. Several communication systems were evaluated on these conditions, and the Globalstar Satellite System was selected to use as the communication system for the beacon. The Globalstar Satellite System is a low earth orbiting (LEO) satellite system and uses Code Division Multiple Access (CDMA) to allocate system resources to the maximum number of users possible. Discussions of spread spectrum techniques and theory, Rake receivers, and error correction codes are included as a background for the design. This thesis examines the initial steps in the design of the transmitter beacon and aims to determine the minimum required beacon transmit power for good receiver performance. A portion of the correlator in the Globalstar receiver is simulated for several scenarios: a single user case with varying transmit power, and a multiple user case with fixed transmit power. Although not likely to occur, the single user case was used to baseline system performance and to verify the multi-user case results. The simulated correlator employed a parallel search strategy and used a truncated version of the Globalstar system code sequence. Finally, a threshold analysis was performed to determine if better receiver performance could be obtained. / Master of Science

The use of practically non-repeating spreading codes to generate sequence-based spread spectrum waveforms is a strong method to improve transmission security, by limiting an observers opportunity to cross-correlate snapshots of the signal into a coherent gain. Such time-varying codes, particularly when used to define multi-bit resolution arbitrary-phase waveforms, also present significant challenges to the intended receiver, which must synchronize correlator processing to match the code every time it changes. High-order phase shift keying (PSK) spread modulations do, however, provide an overall whiter spectral response than legacy direct sequence spread spectrum (DSSS) signals. Further, the unique ability to color the output signal spectrum offers new advantages to optimize transmission in a non-white frequency channel and to mitigate observed interference. In high data rate applications, the opportunity to inject a time-aligned co-channel underlay-based watermark for authentication at the receiver is an effective method to enhance physical layer (PHY) security for virtually any primary network waveform. This thesis presents a series of options to enhance the implementation of arbitrary-phase chaotic sequence-based spread spectrum waveforms, including techniques to significantly reduce fallthrough correlator hardware resources in low-power sensing devices for only minor performance loss, capabilities for programming chosen frequency domain spectra into the resulting spread spectrum signal, and design considerations for underlay watermark-based PHY-layer firewalls. A number of hardware validated prototypes were built on an Intel Arria 10 SoC FPGA to provide measurable results, achieving substantial computational resource gains and implementation flexibility. / Master of Science / This thesis presents a series of options for enhancing the implementation of arbitrary-phase spread spectrum waveforms, a highly-secure class of wireless technologies, in order to reduce design complexity with minimal loss, provide methods for real-time performance adaptations, and extend the traditional application space for increased security of communications in other networks. A number of enhanced hardware prototypes were implemented to provide measurable results, achieving substantial computational resource gains and design flexibility. Given the computational resources and power constraints of devices in the Internet of Things (IoT), the signal detection loss of 2.10 dB for reducing the hardware logic utilization of the brute force fallthrough correlator by more than 76% (and eliminating the need to dedicate computationally-expensive embedded multipliers) is a very reasonable trade. While the waveform is fundamentally designed for increased security, adapting to widespread and/or commercial use may allow some sacrifice of the signal’s ability to avoid interception/detection to improve performance in undesirable operating conditions. In a similar, yet reversed, case, injecting a watermarking signature at the physical layer (PHY) of less-secure wireless technologies for receiver-side authentication also proves to be beneficial.