Clustered wireless sensor networks

The study of topology in randomly deployed wireless sensor networks (WSNs) is important in addressing the fundamental issue of stochastic coverage resulting from randomness in the deployment procedure and power management algorithms. This dissertation defines and studies clustered WSNs, WSNs whose topology due to the deployment procedure and the application requirements results in the phenomenon of clustering or clumping of nodes. The first part of this dissertation analyzes a range of topologies of clustered WSNs and their impact on the primary sensing objectives of coverage and connectivity. By exploiting the inherent advantages of clustered topologies of nodes, this dissertation presents techniques for optimizing the primary performance metrics of power consumption and network capacity. It analyzes clustering in the presence of obstacles, and studies varying levels of redundancy to determine the probability of coverage in the network. The proposed models for clustered WSNs embrace the domain of a wide range of topologies that are prevalent in actual real-world deployment scenarios, and call for clustering-specific protocols to enhance network performance. It has been shown that power management algorithms tailored to various clustering scenarios optimize the level of active coverage and maximize the network lifetime. The second part of this dissertation addresses the problem of edge effects and heavy traffic on queuing in clustered WSNs. In particular, an admission control model called directed ignoring model has been developed that aims to minimize the impact of edge effects in queuing by improving queuing metrics such as packet loss and wait time

An AFSA-Inspired Vector Energy Routing Algorithm Based on Fluid Mechanics

This paper probes into the issue of short network lifetime caused by unbalanced routing energy consumption of wireless sensor network, and discovers that the reason for the problem is unbalanced network load. To tackle the issue, the author constructs a load-balanced vector field by the non-viscous fluid model in fluid mechanics, and optimizes the vector field-based energy routing by artificial fish-swarm algorithm (AFSA). On this basis, the author builds up an AFSA-inspired vector field-based energy routing algorithm based on fluid mechanics. Besides, the author conducts simulation analysis of the algorithm and common routing algorithms. Through comparison, it is discovered that the routing algorithm proposed by this paper has higher energy efficiency than the traditional routing algorithms, which prolongs the lifetime of the wireless sensor network

Experimental investigation into novel methods of reliable and secure on-body communications with low system overheads

Until recently the concept of wearable biosensors for purposes of medical monitoring was restricted to wired sensor applications. Recent advances in electronics and wireless communications have made the possibility of removing the wire from sensor applications a possibility. These advances have led to the development of small scale, wearable, sensing and communication platforms that can be placed on the human body creating the foundation for a Body Sensor Network (BSN). Body Sensor Networks aim to remove the restrictions that traditional wired sensors impose. The anticipation is that BSNs will permit the monitoring of physiological signals in any environment without limitation, giving Physicians the ability to monitor patients more closely and in environments that they cannot monitor today. Even with the recent advancements of electronics and wireless communications there are still many unanswered questions for practical solutions of BSNs that prevent BSNs from replacing traditional wired systems altogether. There is a great need for research into BSN architectures to set the standard for wireless sensor monitoring. In this work a development platform has been created for the investigation into the design and implementation of practical BSN solutions. The platform is used to compare BSN architectures and provide quantifiable results. From this work BSN architecture components that provide optimizations in system performance, energy, network lifetime and security are recommended. In Chapter 3 BSN network architectures employing the use of relaying of creeping waves is investigated. The investigation includes experimental analysis of various test environments. Experimentation demonstrates that the relaying of creeping waves offers considerable performance gains when compared to non-relay networks. For example, relaying is shown to increase network-lifetime by a factor of 13, decrease energy-per-bit requirements by 13 dB and provide the ability for the network to compensate for considerably wider fade margins. In Chapter 4 utilizing the randomness of the wireless channel for securing on-body communications with low overheads is considered. A low-complexity algorithm for establishing symmetric encryption keys is presented and validated. The algorithm relies on readily available RSSI measurements obtained from existing packets being sent and received in the network. The generated bit sequences from the algorithm are evaluated for matching between two communicating parties and mismatching with a malicious eavesdropper. It is shown that the algorithm produces long sequences of highly random bits that are perfectly matched between legitimate parties and highly mismatched with the eavesdropper