ECE Oral Comprehensive Exam for Doctoral Candidacy by Amir Ehsani Zonouz

ABSTRACT:
Results from reliability modeling and analysis are key contributors to the design and tuning activities of critical computer-based engineering systems. In many cases, particularly in smart systems that are capable of analyzing a situation and making decisions based on available data in an adaptive or predictive manner thereby performing intelligent actions, the operation of physical and engineered systems is monitored, coordinated, controlled, and integrated by a computing and communication core, which is based on networked wireless sensors. While the Internet has transformed the way we exchange information with one another, networked sensor systems are taking this stride further to build an environmentally-aware network that will empower us to assimilate a deeper and broader understanding of the physical world than ever. But to ensure reliable and safe operation of sensor systems, it is critical that the communication among these smart wireless sensors be reliable and dependable. Any network outage, loss of transmitted data, or failure to capture important data decreases the users’ trust on the system. From the viewpoint of researchers, developers and even consumers, reliability analysis is therefore an indispensable step before sensor systems can be widely deployed for mission-critical applications.

This dissertation will focus on the application communication of wireless sensor networks (WSN), which relates to the transfer of sensor data collected from the physical environment to the sink node. More specifically, application communication of WSN depends on two important factors: acquisition of sensed data from a specific area, and network connectivity that concerns the reliable delivery of the observed data from sensor nodes to the sink node. We model and analyze the application communication reliability (ACR) of WSN supporting K-coverage in the presence of shadowing for a specific monitored area. The impact of different K-coverage requirements, routing protocols (single-path and multi-path), network density, and channel conditions on ACR will be studied. A prototype software tool will be developed to implement the proposed reliability models and methods for WSN under the application communication paradigm. Additionally, a test bed will be built to validate the proposed research on ACR.

Wireless links are one of the primary performance-limiting factors in WSN. In particular, link failures negatively influence the network performance, reliability, and availability in most cases. In WSN, a link failure might result in the loss of the shortest path between a sensor node and the sink node; thus the data will have to be transmitted via a longer path, leading to longer transmission delay and increased energy consumption. Therefore, it is crucial to characterize the impact of different parameters, such as battery life-time, power consumption of sensor nodes, fading, and interference, on wireless links. Another contribution of this dissertation work is the introduction of a time-dependent link failure model that incorporates the consideration of battery discharge for different type of batteries, sensor node power consumption, and wireless channel conditions. Furthermore, effects of the proposed link failure model on ACR and energy consumption of transmitting sensed data using different routing protocols will be studied.

In this dissertation research, we will also investigate the concept of small-world for improving the communication reliability and energy consumption of wireless networks. Small-world phenomenon is an important property of many complex networks possessing small average shortest path lengths and high clustering coefficients. We investigate solutions based on extension of wireless links...