Agenda

PhD Thesis Defence

• Friday, 28 October 2016
• 10:00-11:30
• Aula Senaatszaal

Relative Space-Time Kinematics Of an Anchorless Network

Space and time awareness has been an integral quest of human evolution, and more so in the currently burgeoning era of wireless sensor networks (WSN), internet of things (IoT) and big data. The rapid advances in technology in recent times has led to affordable, miniaturized and low-power sensor nodes, enabling the feasibility of networks with numerous nodes. These nodes are typically equipped with diverse portfolio of sensors to measure various physical phenomenon, which are cooperatively communicated and processed for appropriate statistical inference. To ensure coherent sampling, efficient communication and prudent inference, the knowledge of position and time of the sampled data is imperative, and consequently accurate space-time estimation of the nodes is as valuable as the sampled data itself.

In this dissertation we address the space-time estimation of a specific class of WSNs, namely an anchorless network of asynchronous mobile nodes. As the terminology suggests, we consider a network of mobile nodes under non-relativistic motion, whose space-time kinematics are to be estimated. In addition, the term anchorless indicates no apriori information on the absolute position or time of any node within the network. This approach is a stark contrast to conventional anchored scenarios, e.g., GPS-based localization, where absolute space-time reference is known. Anchorless networks arise naturally when deployed in inaccessible regions, where an absolute space-time reference is non-existent or only intermittently available. Moreover, when a swarm of nodes is considered, imparting the absolute reference to all the nodes could be limited by communication resources. A few application scenarios include, for example, indoor localization, underwater networks, drone swarms and space-based satellite arrays. In such anchorless networks, it is paramount to understand the relative space-time kinematics, which is the primary theme of this dissertation.

Unfortunately, our understanding of relative kinematics in Euclidean space is inherently dependent on an absolute reference. For instance, consider the first-order relative spatial kinematics, i.e., relative velocity, which is rightly defined as the vector difference between absolute velocities of the respective nodes. However, in the absence of apriori information on any absolute velocities, a natural question arises if these relative velocities can be estimated using only pairwise distance measurements between the nodes. In addition to relative spatial estimation, the asynchronous clocks on-board each of these nodes must also be synchronized, in the absence of a known absolute time-reference. These are some of the fundamental challenges which are addressed in this dissertation.

Overview of PhD Thesis Defence