Design and validation of a scalable Digital Wireless Channel Emulator using an FPGA computing cluster

A Digital Wireless Channel Emulator (DWCE) is a system that is capable of emulating the RF environment for a group of wireless devices. The use of digital wireless channel emulators with networking radios is hampered by the inability to efficiently scale a DWCE to a large number of nodes. If such a large scale digital wireless channel emulator were to exist, a significant amount of time and money could be saved by testing networking radios in a laboratory before running lengthy and costly field tests. By utilizing the repeatability of a laboratory environment it will be possible to investigate and solve issues more quickly and efficiently. This will enable the performance of the radios to be known with a high degree of certainty before they are brought to the field. This dissertation investigates the use of an FPGA cluster configured as a distributed system to provide the computational and network structure to scale a DWCE to support 1250 or more wireless devices. This number of wireless devices is approximately two orders of magnitude larger than any other documented system. In this dissertation, the term ”scale” used for a DWCE is defined as an increase of three key factors: number of wireless devices, signal bandwidth emulated, and the fidelity of the emulation. It is possible to make tradeoffs and reduce any one of these to increase the other two. This dissertation shows a DWCE that can increase all of these factors in an efficient manner and thoroughly investigates the fidelity of the emulation it produces

Doctor of Philosophy

dissertationA fundamental characteristic of wireless communications is in their broadcast nature, which allows accessibility of information without placing restrictions on a user’s location. However, the ease of accessibility also makes it vulnerable to eavesdropping. This dissertation considers the security issues of spread spectrum systems and in this context, a secure information transmission system compromised of two main parts is presented. The first component makes use of the principle of reciprocity in frequency-selective wireless channels to derive a pair of keys for two legitimate parties. The proposed key generation algorithm allows for two asynchronous transceivers to derive a pair of similar keys. Moreover, a unique augmentation - called strongest path cancellation (SPC) - is applied to the keys and has been validated through simulation and real-world measurements to significantly boost the security level of the design. In the second part of the secure information transmission system, the concept of artificial noise is introduced to multicarrier spread spectrum systems. The keys generated in the first part of the protocol are used as spreading code sequences for the spread spectrum system. Artificial noise is added to further enhance the security of the communication setup. Two different attacks on the proposed security system are evaluated. First, a passive adversary following the same steps as the legitimate users to detect confidential information is considered. The second attack studies a more sophisticated adversary with significant blind detection capabilities

Electric propulsion for near-Earth space missions

A set of missions was postulated that was considered to be representative of those likely to be desirable/feasible over the next three decades. The characteristics of these missions, and their payloads, that most impact the choice/design of the requisite propulsion system were determined. A system-level model of the near-Earth transportation process was constructed, which incorporated these mission/system characteristics, as well as the fundamental parameters describing the technology/performance of an ion bombardment based electric propulsion system. The model was used for sensitivity studies to determine the interactions between the technology descriptors and program costs, and to establish the most cost-effective directions for technology advancement. The most important factor was seen to be the costs associated with the duration of the mission, and this in turn makes the development of advanced electric propulsion systems having moderate to high efficiencies ( 50 percent) at intermediate ranges of specific impulse (approximately 1000 seconds) very desirable

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Scheduling based optimization in software defined radio and wireless networks

The objective of this work is to enable dynamic sharing of software-defined radio (SDR) transceivers through the concepts of hardware virtualization and real-time resource management. SDR is a way to build a digital radio that consists of a software back-end for digital signal processing (DSP) and an analog front-end transceiver for waveform generation and reception. This work proposes the use of a virtualization layer to decouple back-end SDR software from front-end transceivers. With this arrangement, front-ends are said to be virtualized, and it becomes possible to share a limited number of front-ends among many SDR back-ends through different multiplexing techniques. In the first work, the hardware/software infrastructure needed for such a system is explored. An intelligent resource management algorithm is presented that demonstrates a potential increase in the number of supported SDR back-ends. The second work presents an exploration of this system\u27s application to aircraft telemetry systems and the potential improvements to reliability. The work includes a reliability model for virtualized SDR aircraft telemetry systems as well as simulations demonstrating changes in performance as hardware fails. In the final work, an improved resource management algorithm based on Markov decision process (MDP) is proposed. This approach addresses concerns wireless regulatory agencies and standards bodies may raise regarding performance degradation caused by sharing transceivers. The process of sharing transceivers causes service disruptions to occur whenever the instantaneous demand for front-ends exceeds capacity. This MDP approach provides a feasibility test and a guarantee that all SDRs can stay within their respective wireless specifications. The proposed technique guarantees Pareto efficient distribution of resources. To make this approach possible, a connection is established between dynamic transceiver sharing and equivalent interference --Abstract, page iv

The 26th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting

This document is a compilation of technical papers presented at the 26th Annual PTTI Applications and Planning Meeting. Papers are in the following categories: (1) Recent developments in rubidium, cesium, and hydrogen-based frequency standards, and in cryogenic and trapped-ion technology; (2) International and transnational applications of Precise Time and Time Interval technology with emphasis on satellite laser tracking, GLONASS timing, intercomparison of national time scales and international telecommunications; (3) Applications of Precise Time and Time Interval technology to the telecommunications, power distribution, platform positioning, and geophysical survey industries; (4) Applications of PTTI technology to evolving military communications and navigation systems; and (5) Dissemination of precise time and frequency by means of GPS, GLONASS, MILSTAR, LORAN, and synchronous communications satellites

Wireless Sensor Networks

The aim of this book is to present few important issues of WSNs, from the application, design and technology points of view. The book highlights power efficient design issues related to wireless sensor networks, the existing WSN applications, and discusses the research efforts being undertaken in this field which put the reader in good pace to be able to understand more advanced research and make a contribution in this field for themselves. It is believed that this book serves as a comprehensive reference for graduate and undergraduate senior students who seek to learn latest development in wireless sensor networks